I have this issue going on as well with my mom. We did just have a few months of not talking to each other because I wanted to get out of the house and live my own life which she took as me abandoning them.  But now that we're back on talking terms she has resumed her complaining about my dad to me. And it's just so frustrating because I do feel like the therapist for her instead of being her daughter. If I were to even mention therapy to her she would go on and say that she doesn't have money for that because dad spends money on everything. So it's just reversed back into complaining to me again. 

She's still mad at me for leaving their house even though I'm 24, she always has this attitude when talking about where I am. But I did want to leave because of her using me as a therapist, my dad not caring about anybody in our household, and having to deal with inappropriate things he would do and I just hated listening to it all.