I haven't seen EL's Formspring account mentioned. It's linked from the "ETC" page on her Tumblr. If sleuthers are looking to her Tumblr for an idea of her personality, why not the Formspring? She hadn't answered any questions in over a year, though:
http://www.formspring.me/mariniere
One question from December 2011 is "How would you describe your personality?" She answered:
"This is a horrible question that should be answered by my close friends.
On my first day of work, a coworker thought I had ADD because I can be really energetic and random. Another person's first impression of me was loud and obnoxious which I know I can be.
I see myself as an optimist but a cynic first. I'm a fiercely loyal friend. I like to laugh but at horrible things like bad puns and black humour. I'm judgmental, hypocritical, uptight but not narrow-minded.
I think most people will find me way too energetic, without coffee. I have my moments of being an introvert."
To me this reinforces the accounts that she was noted by the owner and customers of the bookstore for being obnoxious, and that she could have been that way without mania or drugs. It also makes it more likely that she may have been freely approaching other travelers/residents at The Cecil or receptive to them, and may have quickly jumped into a friendship with the wrong person because of her playful, extroverted attitude.