I have thought about this for a while and I don't believe her manic episode caused her to go up onto/into the water tank. I also don't believe that someone carried her (dead) up into the water tank. Perhaps someone was actually filming her - or getting her to reenact scenes from that movie dark waters, she believed she was just acting (could explain why she kept jumping out of the elevator doing weird things.. if someone outside was filming her). After she got up there onto the tank the person filming either pushed her in the tank knowing she wouldn't be able to get back out or she jumped in as part of the film and the person filming her tried to help her/pull her out (asking her to remove her clothes, tie them together to make a rope) though this was unsuccessful and the person just left her there out of fear that they'd be accused of something.
My thinking based on the facts leads to more or less the same thoughts as yours. I'm thinking she was coaxed into entering the tank by a guy she was attracted to. The same guy she was with on the 14th floor and who led her up to the roof via the disarmed door or the fire escape ladders outside the building.
EL posted a long time in her blog and revealed much about her bipolar condition. There is a high chance that someone took an interest in her. When she opened herself for meet-ups on her trip, this guy could have contacted her and arranged to meet her in San Diego, and then in LA again.
When it was pointed out that this case resembled the plot of Dark Water, I thought it purely coincidental. Movies, especially horror ones, imagine all sorts of scenarios for their plots. There were at least 40,000 movies already made by 2013. So, it was not that difficult to find a movie plot that mirrored what happened in EL case.
But double coincidence is on a different level. What is double coincidence? Say, you and I just met and we found out that our grandmas shared the same birthdate. That's a coincidence with odds of about one in several hundred thousands at least. Suppose we also found out that our grandmas also shared the same date that they passed away. Now, that would be a double coincidence, with odds in the tens of billions. It would be more likely that it's not a coincidence at all, that, in fact, we share the same grandma!
So, back to EL case. It resembling the plot of Dark Water is one coincidence. But, at the same time, EL dressing almost exactly as the character in Dark Water - now, that's a double coincidence indeed! Take a look at these pictures. The screenshots are from the original 2002 Japanese movie, not the remake:
And this...
It is certainly creepy if we believe these are purely coincidental - a double coincidence of the plot and the dressing. So, it leads me to think it is not any synchronicity. I theorise that the guy whom EL met was obsessed with the original Japanese movie. He could be born rich and very free to indulge in wayward stuffs out of ennui. He saw EL's travel as a chance to meet up with her and get her to indulge in his fantasies.
Seeing how EL was playful and smiling in the correct-time video, it seems to me she was playacting indeed. Yes, playacting and reenacting the plot of Dark Water as led by this exciting new guy she met. The black men's shorts that she was wearing, could it be last-minute 'costume' provided by him to her? As to whether the guy deliberately left her in the tank to die or panicked and fled after dumping her clothes in, we can only guess.
To those sceptical, I'm just offering an alternative plausibility based on the facts, and I see this as equally plausible as the theory that she went into the water tank because of a psychotic episode.
There are still lots of unanswered questions, especially relating to the anomalies in the elevator footage. So far, only the slowing down part and the time stamp blurring are explained. I still hope to find answers to the rest, especially why her face was pixelated the moment her full face was tilted towards the camera, and why it was necessary to show yet edit that one and a half minute of extra footage after she had already left the scene.