My dads girlfriend is ruining me and my dads relationship

My parents have been divorced since i can remember; I was about 3 at the time. Mum dated a few times but now she has a boyfriend who I get along with. He has his boundaries and would never come between me and my mother's relationship. But my dad's girlfriend is another story. They have been together since I was about 6 or 7. Before she moved in, I didn't mind her because I didn't know her that well.

About 4 years ago my dad bought a new house and his girlfriend moved in with us. At first it was okay, but as the years went on Its been getting worse and worse. My dad has changed so much because of her. He is now into expensive art, buying things, and having the best of the best. He used to be so down to earth. Its all changed because of her.

The other thing is she NEVER pays for anything. Our bathroom is getting done up at the moment because our bathroom was pretty bad. But shes asking for all this new stuff for it that we don't need! AND now they are doing up dad and her bathroom when it is perfectly fine! All of this is around $90,000. Obviously is coming out of dad's pockets.

When we are going to go out for dinner it's always "Robyn what do you want to do? What about here?" He never asks me what I want to do. And when she doesn't get her way she has a big hissy fit and is down buzz which makes dad change things for her wellbeing. She always says I want this I want that and she always goes against anything I say. My dad is completely on the whip and me and my brother hate it.

We tell my mum absolutely everything and if she wasn't there for us I don't know what I would do. I live with mum half the time and dad half the time. But i am seriously considering living with my mum full time. Dad never shows affection for me anymore; we used to have a father-daughter relationship people would kill for but now its all about Robyn.

Once at a hotel Robyn went to the bathroom and while she was there I told my dad I was cold. When Robyn came back she also said she was cold. So dad spooned her to warm her up. There was me on the other bed, my heart dropped. She also always stands in the middle of us, literally. We would be walking and she would walk in between us, or at a restaurant or couch or car she would sit in the middle. Its so obvious what shes trying to do.

Everyone says talk to your dad about it but I'm not good at talking about things to him. And when we try to he denies it and insists that she is perfect. Can anybody help?