How to get rid of my dad's evil girlfriend?

Im 13 and my parents split when i was 6 years old. i live with my mom and my two brothers but i see my dad everyday. my parents are rele good friends but i hate my dad's girlfriend. they have been dating for almost 4 years. shes a complete jerk and she makes me feel like im fat because she always talks about how perfect and skinny and beautiful her daughters are right in front of me on purpose. and she always hates when my dad spends time with me. they go on vacation together like a million times a year and she is always at my house. she and my dad get into fights everyday and end up screaming on the phone or she texts him nonstop. my dad knows that she bothers me and my brothers but he still stays with her. i read one of his texts one day and all they talk about is sex so i think thats why he stays with her. but my dad and i have a close relationship and i cant take it anymore because she is trying to tear us apart. she can't stand me but she doesnt want to say it to anyone because she relys on my dad for money and pleasure. without him she would have nothing. i need to get rid of this woman or get my dad to dump her. can someone please help me becuase i dont think its rele healthy for me to be dealing with this everyday. thank you so much