At least start distancing yourself from her gradually.

Realize that she has no empathy or consideration towards your feeling. She treats you like an object to dump her negativity on. It is not acceptable. You are a human being who deserves to be treated with dignity and respect.

Distancing yourself from her is also in her best interest:

She needs to learn to stand on her own two feet. You want her to succeed.

She needs to learn that being toxic has consequences--losing friendships. Without consequences, she may never take her mental health seriously. By accepting her, you would be reinforcing her behavior.