When 2 Let go & put yourself first

I struggle. The depression and nights with lil sleep hurts. I just want to be normal. I joke around but deep down not feeling so good. I moved and left my family 2 help a friend who burned all resources & said she needed me. She is sweet and I love her. But I can't take this I miss my family. I think more depressed because I don't want 2 be here. Her OCD and issues with dieting drive me nuttier.
How can I tell her that I want to go home but not disappoint her.
Thx