Toxic Family Member

I’m needing help with a model and in figuring out how to change my thinking. I have a sister who grew up in competition with me. My mother fostered that competition. My sister continuously reacts to me in rage or anger or is just plain mean. She uninvited us to her daughter’s high school graduation. My daughter was given my aunt’s old car and my sister came over to our home and literally drove it to her house so my daughter couldn’t have it… the list goes on. When someone is repeatedly toxic how can we enforce boundaries (ok to cut them off?) or change thoughts? This situation causes my family great pain and stress.
C: My sister
T: She’s mean to us
F: Upset
A: Ignore her
R: She continues to be mean
I’m wondering how to change my thoughts on this. Clearly I have a manual for her (aka. don’t be mean). Anyway, would love your help.