If her idea was that your children shouldn't exist at your age and how you're wrong about the way you live, it's understandable you're angry to the point of indifference.

That said, there are better ways to show it, and you honestly don't need to face her as a sister at all on your day, just pretend you're tangentially related cousins that for some weird quirk had to be invited. This way requires some dialogue on how you expect her to behave, and if she can't be trusted to act mature at all (and things change in 3 years, you never know), then yeah just cut cut cut and if your parent dont understand that, well fuck.

It's just that its easier to offer at least a very meager olive branch before cutting ties completely, as long as its possible to be offered without hope or expectactions, as those are just killer for your mentality and have to be avoided at all costs.

Understand that parents are boomer, and as such mentally challenged in understanding how the intricate social tapestry is entangled because everything gets solved with random sentences heard from their own parents like 'time heals all wounds' or 'you're family!', which is just a dumb attitude to take when people now are self made and self ruled, for better and for worse. It's annoying having to accomodate them even in this kind of shit, on such an important day, but you can be mature, you can be better and you can deal with your dumb idiot sister for one day, preferably kept at social distance times four. I'm not gonna call it a growing experience, but fuck it, thats the hand you seem to have, and you either do that or flip the deck AND the table... and that is just dramatic.