I'm going to ruin my girlfriends birthday
Could you explain to me why you want to ruin your girlfriend's birthday?
She made me mad. I want to ruin her perfect night with her family.
You shouldn't ruin your girlfriend's special events like birthdays. She'll end up breaking up with you. If you're mad, you should talk to her about that and be honest.
I want a perfect revenge and to ruin her happiness because it'll make me happy.
It shouldn't make you happy to hurt a loved one, and even though you're mad at her right now there will most likely be a day very soon where you've forgiven her and moved on. Wouldn't you want her to be happy so that this day can come sooner and the love can be rekindled?