What should I do about mom?

My gf and I have been together for 2 yrs. and her and my mom have never gotten along. They don't get along because my gf is black (dominican and puerto rican) and according to my mom "all black people are bad people". Recently my gf and I told my mom that she's pregnant, and my mom wasn't happy about the news at all. She even went as far as calling my baby a "n*gger baby", so eventually my mom ended up getting cussed out. I have done a lot for my mom (pay her bills with MY money, fix stuff for her, clean, etc.) over the past few years despite how she has treated my girl. Why would she continue to act like this knowing everything I do for her and how close I am to giving her the boot? Should I just cut all ties with my mom?