good to hear from you again.
it does sound very serious re your friend. and i can understand your fears. does your friend have family where you live or you have met them? if so it may be helpful to let them know what's going on with her. perhaps they would intervene. and you're correct you are helpless to help her. but telling her about your concerns re her could help. justme but i'd ask her too if she'd be willing to get help.
your fears re yourself-falling back into harmful habits would prevent your helping her too. and you don't want to self-sabotage yourself by resorting to this old behavior?
focus on noticing the shift in your thinking. it's an escape resorting back to the old "solution". often the old habits return if we don't heed to the fact we're slipping and do something to change it. otherwise the "insanity" will return.
please let us know how u are doing. i'm glad you're reaching out. plus i hope your friend will get help too.