Every time she calls, it's to vent, and I just keep validating, not agreeing so much us putting myself in her shoes and it seems to keep the peace. 4 weeks now.
Learning the skill of emotional validation is a really important helpful skill; people who feel felt usually stay calmer, it increases ownership of what is mine v. what is yours, and it can enhance connection.
I don't know exactly what to make of your descripiton, though, of what is happening. Is listening to this person vent fun or satisfying for you?
Emotional validation is a way to help people feel heard ; that you understand how they feel.
It's not meant to be you providing a venting service on demand; your own boundaries and limits are still important. Venting ad nauseum is not helpful or healthy for either one of you.
What are you getting out of this?