Ex girlfriend coming to Thanksgiving dinner

My SO has a 15 year old with someone else. She' throws slurs At me and tried to ruin my holiday a few years ago and I almost left my boyfriend because of it. He asked his parents to stop inviting his daughter's mother but they do anyway so we didn't go to Thanksgiving and his family acts like I'm in the wrong for my feelings because his daughter and her mother brought a gift for our baby. I feel like they disrespected me and chose her over their grandson's first Thanksgiving. Should I let them see my son anymore?