So many good questions posed on this thread. I have extensive 3+ season hiking experience in this area, 88 of the New England Highest Hundred peaks and hope to finish up all 100 next summer. I don't winter hike in the big mountains, but I have hiked into late November and even a few December/January hikes when the weather is good. Lots of people saying her attire doesn't make sense. I agree with that on the surface, but when I read what they're saying she was wearing I'm reading a very vague description. "Brown jacket, exercise pants, sneakers" is not that far off how someone would describe me when I'm headed out onto the trail. No report of any kind of pack? The jacket could be just the top layer of multiple layers, reports haven't been more specific. Exercise pants could be thermal tights with appropriate underlayers. Sneakers, that's the footwear I use (I will pack micro spikes when appropriate, and I am not hiking in deep snow). I hiked Owl's Head, which is the peak immediately east of where Ms. Sotelo was, in November 2016 with a little bit of snow on the approach trails and up to a few inches on the slide path, wearing Brooks Cascadia running shoes (no microspikes), running tights with a layer underneath, multiple layers on top. No issues. From what I've seen the last decade, I'm going to say around 40% of hikers, even 4000'ers including the Presi's, are wearing running shoes or footwear that's a lot closer to running shoes than they are to hiking boots.
A few people questioned why she was dropped off. If her plan was as it's been reported: up Lafayette, then south on the Franconia Ridge Trail across Lincoln, Haystack, Liberty, then to Flume - it would make sense that she planned to descend from Flume rather than hiking back north towards any of those other peaks. In that case, the plan likely would have been for her Mom to pick her up at the Flume trailhead which is 3-4 miles south of the Lafayette trailhead. I find that ridge pretty mellow, and it does drop almost 1000' from Lafayette to Flume (with of course climbs to summit the intermediate peaks). Overall this is a long hike. It's about 4.0 miles up Old Bridle Path and Greenleaf Trail to Lafayette. It's about 5.0 miles from Lafayette peak to Flume peak on the ridge. It's about 4.8 miles from Flume peak down the Flume Slide Trail to Liberty Spring Trail to Whitehouse Trail. I've hiked the Lafayette/Lincoln loop (the northern part) in 4:09, and the Flume/Liberty loop (the southern part) in 4:36. I'm a pretty fast hiker, and for me I'd conservatively estimate 7.5 hours in good weather for the loop Ms. Sotelo was said to have been planning. But for a lot of hikers, even in good weather this is going to be a 13-14 hour hike. And the descent of the Flume Slide Trail is a very challenging descent even in good weather.
One thing I'm curious about that I haven't read anything about yet... When her Mom dropped her off at the Lafayette trailhead, I wonder if her Mom stuck around that trailhead for awhile, or if she went somewhere else to wait out the interim until she had to go to the Flume Visitor Center lot to pick up Emily at the end. If she didn't stick around the Lafayette trailhead area, is it possible Emily started out, got a little way up and figured she wasn't properly prepared, turned back and ended up where her Mom wasn't? You would think Emily would have made a call if her plans had changed like that, but cell service in that area can be spotty. There are options to walk parallel to I93 (Pemi Trail on the west side of the highway) to get from one trailhead to the other. Also possible she would have tried to get a ride, which brings in a whole different element. If her Mom drove off, planning to pick her up later at the bottom of Flume, and Emily decided to turn back partway up Lafayette, we could be looking at a multiple hour time gap that she was around those trailheads.
