I left the Christmas party because my girlfriend knitted a full blanket for her male best friend
What emotions did you experience when you saw the blanket?
I was so angry because it seems like she put in so much more effort for his gift.
I think that it is okay to be upset, but you still should have stayed. It is wrong to leave the Christmas party early, it is an even that only happens once a year.
I'm going to leave again next year if that is okay with you. Also I want her to make me something.
Again, I can understand your frustration, but maybe your girlfriend didn't think this gift was such a big deal. She might just enjoy knitting for its own sake, and gave this gift to her friend as something minor. You were overreacting by leaving early, and might have ruined the party for her.