The Struggle of Being Friends with Someone with Severe Mental Health Issues

I can't really give much input on the situation because of course I don't have all the details but you are never obligated to be friends with someone

the best thing i can say is, set firm boundaries. encourage them to do the same. failing to set boundaries is how situations like this start. if you don't set firm boundaries they will end up depending too much on you, in this case emotionally, and it's a surefire way to set the relationship (friendship or otherwise) to fail. it's a lesson i learned only when it nearly killed me. it doesn't matter how bad you feel for them. you and your own mental (and physical) health has to come first in every relationship.

I have a hard time keeping friends too, and taking to my therapist about how to regulate and minimize negative reactions that are intensified by my mental health issues has really helped. People don't have to stay by us if we hurt them, even if it was bc of a symptom. It suck ass, but maybe now is the time to learn how to enjoy spending time with yourself, and have dedication to improving your quality of life and your mental health. Then maybe once you cope better it'll be easier to keep friends. Its a hard truth but if people don't want to be friends with you bc of your mental health, you aren't doing what you need to to take care of yourself. I learned this the hard way after a huge breakdown and I lost a good friend of mine

This isn't (or shouldn't) actually be about their mental health issues. Its important for them to understand that mental illness doesn't excuse all behavior, and for you to understand that mental illness doesn't mandate you remain in a relationship that is hurting you.