It's All About Her

I never liked my dad's girlfriend and told him how I felt about him getting married to her and I recently discovered he is not listening to my brother and I about how me feel. She makes everyone of my important events (i.e my own birthday party and my graduation) all about her.
I never liked her and now i think she doesn't like me either because i'm the only person who openly thinks she's wrong for my dad. Two days ago it was my family birthday party and everything was going great until present time. i was polite and thanked her and her mom for the gift but apparently she "didn't hear it" and felt ignored so she got my dad to yell at me. my dad was sitting right next to me when i said thank you for the gift he even heard me but when she wants him to do something he does it he turned his back on his own daughter. Even my brother who was sitting far from me heard me say it but apparently dad didn't hear it either. He took me inside and yelled at me calling me "just like my grandma!" and that he would cut me from the family also that i was a *****. All the while she was standing in the corner grinning and knowing that if she says one more thing i'm out of the family.