I'm going to ruin my mother's relationship with her boyfriend
Why do you want to ruin your mother's relationship?
She made fun of me for being so dysfunctional with regards to dating girls.
Your mother should have never made fun of you, but you shouldn't try to ruin her relationship either. Do what is right and leave her relationship alone.
I'll do what I want and I want to destroy her.
Your mother's relationship is not your concern and interfering in it is wrong. Try to forgive your mom for her mistakes with you early on and love her anyway.