Stressed and confused. Need some help, insight, or advice? (warning: this is very long)?

Sounds like she stole your phone, probably to try and find out any dirt about you from your messages. maybe if yuo have another party and shes there she'll put it back when no one's watching. Keep an eye out though, she sounds like she could be trouble. Get your guy to talk to her, but if she does offer to give it to him make sure you go along to so nothing bad happens. Sometimes, guys can't help themselves. and a little alcohol never helps.