Now is when you're starting to see the negatives about a person.

Unfortunately, its not enough to like or love someone. That's not enough "glue" to keep a relationship together.

Her negativity will indeed take you lower and lower. If all she does is vent about her problems to you, and says that without venting she has nothing to say to you.....is it a stretch to say you two have nothing in common? Because if you two had things in common then she would indeed have other things to talk about.

I had to break up with someone who had something negative to say each and every time I opened my mouth. I couldn't handle the constant negativity and had to break up with him.

I would encourage her to seek out more therapy.

It may hurt her, but I think it would be a good idea to be truthful and tell her that you cannot handle constant negativity.

Unfortunately she may not be in a good place right now to be in a relationship.

Hugs.