I would prefer for my twin sister to not have her thirtieth birthday without me.
Why do you want to go to her birthday?
She is really the only one in the family who I feel loves me.
That's unfortunate, it is rude to exclude family. You should talk to your sister about why you weren't invited.
I can't believe she doesn't love me enough to let me in her huge place, damn her.
Well maybe it was just a miscommunication or a mistake. May be a good idea to give her the benefit of the doubt until you find out why you were not invited.