Not weird at all. Enjoy the event!
This situation did occur last year and my wife (and I) didn’t go because we weren’t invited plus it was 3,000 miles away. Even if my wife was invited, I don’t think she would have gone anyways because she’s hands off with the D’s life other than paying the tuition.
If my kid’s (imaginary) girlfriend was graduating, the only way we would go is if my kid was in the same graduation. I would ask my kid first if it was ok to go and I’m 100% sure he would tell me to take a hike. In fact I’m almost sure he wouldn’t go himself unless he was forced to go, he can’t sit still anywhere.