how do you help someone help themselves?

do you talk to them about it even when they wont listen?

do you tell a teacher or adult even though they made you promise not to tell anyone?

do you keep it all in while it breaks you down and just let it?

do you pretend the situation doesnt exist or laugh it off like they do?

i don't know what to do, and its stressing me out to the core.

because what she's doing isn't healthy but when i say something her response is "im not suicidal" which she isn't but it doesnt make what she's doing any less of a problem.

how do you help the one that needs help but won't let you help them?

i've been thinking of what to do all weekend but i have no answer.