Sounds like this is more about your relationship with her than her choice. I say that because you talk about how she can speak her mind but you aren't given the same space in the relationship.

I agree with what people have said about it being too hard to know what the process has been between them. My sister always complains about her husband but I finally realized she complains most to me. There are other aspects of their relationship but I'm her go-to for every little gripe she has about him, ugh. From what I hear from her it sounds like she hates her husband but I see I'm the recipient of only this one side.

I also think she's upset by her decision and taking it out on you.

Maybe this is a good time to evaluate what you want and need in friendships and see if this one can work with your model of healthy. Regardless, I hope any ill feelings or hurt is processed and passes in a way you feel better about things soon!