Hello. I'm new here, and wouldn't normally contribute, but if it can somehow help, then it's at least that
First of all, understanding the situation she may have been in, and where was and where she is going.
Reviews say there are no toilets in the rooms. Reviews say there are communal showers and toilets on each floor. The video is at night? She appears to be dressed in a very casual way, I believe she went to the communal toilet (not the shower itself as she has no items with her). I have to say I don't think she was on drugs or anything like this. I also believe that she has felt uneasy, either due to someone's presence soon before the video started, or in previous events when going to the communal toilet/shower at a previous time during her stay.
Some believe she is on the 14th floor in the video, and her room was on the 4th floor. I think it makes sense: she did not want to use the communal toilet on her floor as a safety precaution, this way if there is any creep she can take the elevator to her floor instead of going directly to her room, so she went to a different floor far from hers to use the toilet. This may even be a helpful tip she got from another guest.
When she enters the elevator, she does not appear to be quite in fear at all, and she pushes all the buttons in the center row of the panel in a rather casual way.
This is what the panel looks like:
So she is on the 14th floor, her room is on the 4th, and we see she hits seven buttons: the 14th (light doesn't turn on, because she is on that floor already), all the way down to the door hold button. I think she didn't realize she hit the door hold button at the end.
Why push multiple buttons? That one has been a big puzzle, but if she has been creeped out on a previous occasion, or in fact just a short moment before this video in the communal toilet, it makes sense. Here is what I found:
Travel Crime Prevention Tips
Elevators
• When riding on an elevator, always stand next to the elevator controls.
• Do not enter an elevator if it is occupied by anyone you consider to be suspicious.
• If someone is watching when you enter an elevator, press several floor buttons so they will not know which floor you got off on. Notify the front desk if the person made you feel uncomfortable.
It is likely that a girl who travels solo for the first time would have looked up such safety tips before leaving. She might be thinking that if the person walks into the elevator with her, the person will look very suspicious if they disembark on the same floor as hers, but more importantly she can head for the stairs after getting off on a floor that isn't the one of her room, leaving the creep in the elevator, and then walk to her actual floor. This is to do as it says in the tip, which would prevent him from knowing for sure which floor is hers.
This picture shows how the hall looks, at least on one of the floors (which appear to all be pretty much the same in terms of layout):
From inside the elevator, she can see into the mirror slightly to the left of it. That's why when she is inside, she is often looking towards the wall to the left outside the elevator: she is looking into the mirror to see what is outside to the left. That's why when she actually stands to look outside, she looks rather intensely to the right, because she already saw to the left through the mirror. The right side is the "dead angle". When she leaps out, she also first looks to her right. Even at the beginning when she first enters, she places herself in a way that allows her to look into the mirror and see to the left. In fact I wouldn't be surprised if the toilet is to the left of the elevators past the corner shown in the picture above. She probably came from that side before calling the elevator, and if she felt watched it makes sense that she placed herself in a way to see that angle while in the elevator.
Now I think body language also tells a lot here.
First she stands in the right side, looking in the mirror, waiting for the doors to close. They don't close. She is starring in the mirror as she moves forward, before peeking out quickly (right, left), then immediately steps back in, putting her hands together (instinctive sign of feeling intimidated/scared, trying to make herself small), but standing right in the middle and straight; a position that doesn't make sense for someone trying to hide, which she rectifies immediately by standing on the side, but always while looking into the mirror outside. Realizing that if she can see outside through the mirror, someone outside could see her too, she steps into the corner: now she can see nothing but cannot be seen either.
After a short pause in the corner, still holding her hands together, she does something that from my perspective is rather brave in such a situation; she decides to get close to the door and lean on it to look outside, but notice how she focuses on her right for some time, exclusively. This indicates to me that she no longer considers the left side to be where the presence may be coming from, after having been looking in that direction all along. She is puzzled and hence decides to peer to her right instead, which she couldn't see through the mirror. After as short moment, she turns her head slowly to the left to look into the mirror.
From here, it appears that the right side is dismissed.
Still looking leftward into the mirror and having peripheral view of the hall to her left, she steps forward slowly, trying to get the best view she can of the left side, hands still together, until she does a little leap forward.
The leap itself indicates to me that she made contact with someone. Notice her hands remained together during the leap. The leap didn't give her enough range to see more than she would have without simply leaning further from the "safety" of the elevator, so it appears to be a reaction. It is a mix of trying to react to a presence in a way that is both confrontational (leap forward, like trying to scare an animal away), and a result of being startled. She never looks to the right, so it truly appears that she is making eye contact with the source of her worries.
Notice how even after this reaction, her hands are still held together, and she almost immediately straightens her back. This to me indicates that she has conflicted feelings about who she is seeing. Notice how she then opens her legs to take a very stable position (standing her ground), then brings her legs together again and turns her head rightward slightly (still oriented leftward in relation to her body) as if tracking the person walking towards her in the hallway. She is switching from confrontational/standing her ground to a more intimidated position, feeling afraid as the person approaches she steps back into the elevator, (the person probably stops walking forward in reaction to her stepping back, not wanting to scare her). She then steps out again while looking to her right at the same time, indicating that the person who is right there is NOT considered the threat she has been worried about and is therefore doing one last check to her right to make sure the original threat is not there since she hasn't looked in that direction for a while, before now getting close to the person (feeling secure, talking to a woman going to the toilet perhaps, or another female guest or an elderly?).
I believe at this point she is no longer afraid. Her hands finally let go (they have been together since the very beginning when she decided to hide), as if relaxing, and then she even puts them on her head, as if becoming even more at ease. I think she is now talking with the person.
After a brief conversation, Elisa steps back in the elevator (notice she appears to be smiling), hands touch the walls, looking tired/relieved/exhausted from what she has just been through emotionally, and maybe feeling silly, and it can also be considered an instinctive mannerism to attract empathy. She keeps hitting the middle row buttons numerous times out of desperation, but the elevator won't budge. The person still being outside nearby, she walks out talking to her, giving up on the elevator. Notice she stands with her back directly to the elevator buttons, signifying to me that the other person isn't looking to use the elevator, and is standing right in front of her (occupying the center space of the hall, hence why she is standing so close to the wall). She talks to the person, and waves in front of the elevator (again appearing to be laughing/smiling at the situation), explaining it won't close, and then she appears to explain something she is listing on her fingers or pulling backward on them (a way to remove stress?).
She drops her arms, as if done with the situation, and walks away. The doors finally close.
Note that it is possible that there never was anyone else, but this is the impression I have. One of the main reasons I think she sees someone when she leaps out is that she never again bothers with the right side to any extent, everything from that point on happens to the left. If she felt threatened and never made contact, there is no reason why she would have ever stopped worrying about what is to her right.
Also, because of her body language; hands together all along, until a sudden very relaxed attitude, as if all fears were gone.
Hopefully this may help. Hoping this case is solved, so the family can heal.