Best friend's mom is a b? LIVID.

So I've known my best friend since we were 12. The first time I ever went to her house, I noticed her parents were off. Her mom didn't seem to be all there, and I was smiling and being very polite and she was basically just being very, very rude that shouldn't be normal when you're meeting someone for the first time. As the years have gone on, her parents have kicked her out numerous times, refused to let her live a social life or do anything as a teenager, treated her badly and called her names, made her lose weight, thrown out her things randomly, refused to pay for schooling, etc. She'd call me crying asking if she could move in with me because her parents wanted her gone permanently. My family took her in. We gave her a bed in my room. We drove her places like job interviews, to the gym, to work, to her boyfriends, etc etc. We took her on vacations and trips with our family. She's in all our family photos and comes to all the family gatherings. We got her passport papers for her and drove her down to give them in because her parents wouldn't. My dad has basically treated her like a second daughter and has done everything for her he would me and my sisters. We've always called her my adopted sister. When she turned 18, her parents kicked her out and told her to get a student appartment. We helped paint everything and buy her everything for the apartment. I've literally been around her mom maybe twice, but because she was so rude to both me and her own daughter, I stopped going around her house when we were young. She would beg my best friend to ask me to share her quilting company's posts all over Facebook, which I have been. I don't agree with the way she treats people, but she is my best friend's mom after all. The only problem I can actually think of is one time, my best friend begged her parents to let her go to my uncles birthday dinner. They said it was fine. It's 2 hours away. We were there for an hour and her mom calls and says for literally NO particular reason, they wanted her home. She kept asking why and she would say because we can tell you what to do. Obviously since we were at my uncles birthday party 2 hours away, my dad couldn't just get up and drive her home, especially since we just got there. We were only 15. He said we'd be home as soon as possible. But I guess that wasn't good enough.