No! You are not and cannot be her therapist and trying to help her will be a roller coaster most people do not have the skills or strength to deal with.
Source: I have depression and before I was on meds I was a real poopie pants. I can hardly blame people for not wanting to be around me. I wouldn't want to be around me like that.
Also, when I broke up with my one gf she was suicidal. At least I had some experience with this so I got her help within minutes.
I have a long time interest in psychology, specializing in relationship dynamics for 30 years.
(Please note, we give the best advice we can based on the information given in a post. For better advice, please include the age of all romantic partners.)