Am I doing the right thing?

My girlfriend and I have been together for 2 yrs. and her and my mother have never gotten along. They don't get along because my mom hates my gf because she is black (Dominican and Puerto Rican). My mom seems to think "all black people are bad people". A couple weeks ago me and my gf told my mom that we're having a baby and she wasn't happy about it at all. She even went as far as calling my baby a "n*gger baby" and I wasn't having that so I blew up and ended up cussing my mom out. I have done everything in my power (counseling, talking, fighting, etc.) to prove to my mom what a beautiful person my gf is, but she just doesn't want to hear it. So for my families sake I decided to cut ALL ties with my mother. Am I doing the right thing?