I'm not going to give my girlfriend my two extra tickets for graduation
How do you think that she is going to feel about that?
She will be mad at me and bitch about it.
I understand wanting space from people sometimes, but there is no reason to not invite her. Doing this out of spite could potentially ruin the relationship.
She will just have to get over it.
If you have no one else to give those tickets to, why not give them to her? It seems a little selfish to keep those two tickets for her, she just wants to be there to support you.