Is NOBODY wrong in the post ? POST : Throwaway account

My GF(25F) and I(26M) agree that her family has issues with picking favorites. The brother has had 2 cars bought for him. My GF's sister has had one car given to her. My GF was the first in her family to have to take a loan out for a car. Oldest brother had 5 years of college paid for, neither of the sisters did. Took an extra 4 years for my GF to get her license because she's the only child her parents didn't teach - she eventually saved enough money for an instructor. 

GF just finished college and is trying to get a job together so she can scrape up enough money to make payments on school/car loans, and move out of their house and in with me - but as a teacher where we are it's been difficult. 

Recently, my GF's mom had to give up her drinking addiction, but now the parents are taking vacations 1-2 times a month to go gamble. I can tell this has been affecting my GF. Especially because they ask my GF to "babysit" their dog. By the time they ask (maybe a day or two in advance) they've already planned the vacation and have "no other options" at this point. So my GF has to cancel any of her plans and stay at their house so they can go gamble. I've told her to just say no, but her parents are very good at convincing her. 

The final straw came when my GF told me that her family was leaving to go gamble for the three days before Christmas. She'd be stuck at home alone watching a dog for 3 days, while I'm busy with the holiday plans that were already made. 

We both agree that when she moves out she'll be much happier. My real question is about the fact that I didn't go to Christmas at her parents' house. I felt that they chose gambling over family, and would do so again in a heartbeat. I also felt that SOMEONE had to tell them "No". 

I let my GF know ahead of time that I wouldn't go, that I didn't feel comfortable around her family, and that I was sorry that she was caught in the middle of it. I've also expressed a number of times that I think her family is still suffering from different forms of addiction and I think her agreeability is helping enable it. 

She was already upset that she'd be stuck alone, and was feeling down about her family. We planned to celebrate Christmas at both families' houses on Christmas. She still came to my family, and has been very upset that I didn't come to hers. 

Since then she's said that she's not going to tell me anything about her family any more, which I think also means she doesn't have anyone to vent to. Should I have put these feelings aside for one day and spent a few hours with her family? Or am I justified acting on the things she tells me about her family? 