Don't take it as an insult, it just matters for context.
23 is very young. And since you have your whole life ahead of you and you aren't seriously invested otherwise in this gal, it affects the advice we give you.
If its bulimia, that means she has pysch issues. At minimum. Not sure you want to go down this path. Anyway, Vash will have more specific info for you.
But, more generally, what is it you hope for with this gal? Why your post?
Weird that she won't tell you more. She's either a drama queen or just very private.
Second thoughts can generally be amended with judicious action; injudicious actions can seldom be recovered with second thoughts.
--Cyteen by C.J.Cherryh