I just cannot with this woman anymore

My stepmother, good Lord. I don't even know exactly what it is but I've known her since I was...5? And have never liked the woman or gotten along with her. After my dad and I had our falling out however many years ago I told him I was never comfortable around her and didn't want him to take it personally that I never wanted to spend time there. I love my dad and I love my brother and want to see them often but there's Kate to deal with. She has said some horrible things to me in the past few years to the point that Paul will even speak up and tell her politely to shove it. And my dad was like "why didn't you ever say anything? Why didn't you just leave if she was like that?" but I told him "because you're my dad and she is your wife. I don't want to hurt your feelings nor do I want to give her the satisfaction of seeing me make a scene" So now unless it's a family gathering I just avoid her. Dad and I will go out to lunch or dinner, James is a grown-up now so I can see him whenever. But one of the things she's taken to bitching about over the past couple years is that she'd never come to Paul & my house, despite us having events there that she was invited to. We didn't entertain like dinner-party-wise there because that house just didn't lend itself to such things. So here we move into this nice big house. James has been here a number of times, Dad has been down. And it's Father's Day so I invite Dad down for a barbecue. The butcher shop nearby has Kobe steaks, so I splurged and got steak for all of us, including Katie since I had checked with James to make sure she was coming. Then today, only Dad & James show up. So you know what bitch? This one is on you. You were invited, you were provided for, and you chose not to show up. It made the day far more pleasant for me. We ate fancy steak, we drank margaritas, we watched Archer and had a good time. If James gets his way and makes me follow through with my (STUPID) offer to host family Thanksgiving this year she had better show up and steer clear of me. I'm done trying, even on the most pedestrian level.