I'm not a cunt, I have solid reasons for this. They're toxic and hateful and I am the only person in my family who doesn't just ignore their shit or brush it off.
I just found out that my mom is planning on going by my grandparents' at lunch tomorrow, after I had told my grandparents I was dropping her off.
So, my options are either let this slide and have it absolutely come up in the future as a "well it was okay that time...", stay for 3 extra hours to supervise and put up with my mom and/or sister and probably end up calling my therapist in hysterics at some point in the day, or be a massive cunt and back out of DD staying over there with no advanced notice and deal with getting the cold shoulder for a week or two from my grandparents for being such a hardass.
I'm seriously leaning toward just sticking around to supervise and dealing with the emotional fallout later but FFS I hate this shit.