Were you up front? Did you say you were going to spend the weekend with KA unless something better came along? When you make plans with someone, it is rude to go do something "better" that comes along after you made the original plans. That is just plain manners. Do you have FOMO, STP? Are you so afraid of missing a possibly great party you would throw manners out the window if you hadn't been truly up front?
If you DID tell KA you'd hang out with her except if something better came along, then you made it clear. If you told KA that you'd hang out except for this party when you originally said you'd hang out, you also made it clear. If that is the case, you do as you said you would do and also reap what you have sown. If you don't want to be beholden to anyone, then why should you care what KA wants or thinks?
If you DO care about what she thinks and feels, that doesn't mean she "controls" you. She is also free to tell you what she thinks and feels. Then, if it's a healthy relationship, you work it out. If you didn't really make it clear this time, make sure you do next time. Agree to stay at the party for x time and return by y time. Yes, that's a commitment. Are you up for that or no? If no, be clear about that.
Saying "I'm going to go where ever I want whenever I want, and I don't care how you feel about it" is clear. Saying "I'll hang out at your place with you and your D" is also clear, as there is no "except" clause. Deciding after agreement on plans that you want to change the plans for you is poor manners and you can expect that the original person you had plans with will be disappointed and unhappy.
If you wanted to go to a party or what have you when you had no plans with KA, then if you want to invite her to go with you, you do. If you don't, then you don't. If she can't go, sucks to be her, but life goes on. If she doesn't want to go, her choice.
How the situation came to be matters, not just if she can or wants to go. Were you 100% transparent and honest? Did she change if she wanted you to go if she agreed you'd hang out unless something better came up? It's not just cut and dried based on one person not liking the other's response.