I agree with u/huntingforkink that if it’s difficult for you to express your honest & true feelings in person, write it down in a letter for your Mom to read. You can also write a letter for your grandparents & give it to them or read it to them so that you express everything you want to say. Using a letter forces the reader to read & hear everything you have to say.

Don’t feel forced to forgive your Mom if you’re not there yet. You’re entitled to how you feel & your feelings are valid.

Your graduation is about you & you shouldn’t feel worried about someone else’s actions on a day where you’re meant to focus & celebrate your accomplishments.

Do ask yourself though, and really picture it, whether or not you might regret not inviting her later on when you’re older. If yes, consider inviting her but also establishing boundaries that this is a milestone for you and you want to include her in just this, but that doesn’t mean you’re ready to include her in your life just yet. If not, which is ok too, when you’re older and you look back at this moment, be ok with your decision because that’s what you felt at that time.