Annoying best friend...

I'm so frustrated with a friend of mine. I dropped everything to help her and it's never enough. I feel burnt out. But I love her dearly and I want her to do well. It's just UGH I needed to vent somewhere that she won't see this. She is fully aware of her problems but does nothing to fix them. She has diagnosed mental illnesses but willfully chooses to forgo medication or therapy, even though she is constantly miserable. She only talks about wanting to die and how she hates everything. I'm a much more optimistic person and it's just so draining to be around her. Idk what to do.