I just went back and reread your first thread.

About the triggers - anything can do it really. Being a teen is very stressful, it could have been some ho trying to steal her bf or a teacher may have embarrassed her. They are so uncertain and easily hurt (though all the attitude).
Mix in an eating disorder and the complexities are magnified SO much.

Hopefully longer term councelling or support will keep her on track for awhile - are there any teen confidence/leadership programs around?