As you have said, you don't like her, why exactly is it you wish to go so badly then? To support and celebrate her graduating and extend an olive branch in the hopes of having better communication and improving your relationship, even if not for your sake, but for your husband? That would be the most logical answer, if it were true, it sounds like you planned (with a full itinerary already) an entire vacation and somehow need to fit in her graduation around your plans. That's not at all what this is about for your husband, not sure if you really see it or not.

I'm sorry but it does sound like jealousy, as others have said, that goes much deeper, even some envy of her if I'm being perfectly honest. I consider those who have their education paid for by their parents extremely fortunate, certainly not entitled which you haven't given a single example of here?? But "apparently she makes up for it by supposedly being smart", this says a lot and is very demeaning and insulting, do you speak to her this way, and if not, people pick up on behaviours and when someone clearly dislikes them. Did she actually slander your job, or simply inquire why you didn't pursue law? (Just curious since it feels you could be skewing things in your mind with your feelings towards/against her.)

Regardless, being excluded, where friends and family will be, I'm guessing bothers you too, but it's just not about you. At this point, you are both adults and I can see why she would not want someone who doesn't care for her at a celebratory event in her life. Obviously attempting to mend things would be in everyone's best interest, if that's not optional to you, then I think it's time to be civil, and move on since being insulting to your husband's daughter won't will definitely not work in our favour.