I don't know how to make my girlfriend better. I'm not good at helping others.
Would you mind telling me how you want to help her get better?
No, I don't want to talk about it anymore. I changed my mind.
It is noble to show concern for your girlfriend.   You should not put too much pressure on yourself to solve all of her problems,  It is not realistic and could make you depressed.
I'm not thinking about myself right now. I know she will get over this.
Just do what you can and show support and that is the best that you can do. You don't need to beat yourself up over it, just try your best.