I'm thinking of ignoring my girlfriend for a week
I hope you're kidding, is there a reason why you would ignore your girlfriend?
Yes, because I hate the bitch
You shouldn't pretend you don't have a gf for a week. What if she takes it badly and just leaves you for another guy.
I don't give a shit because I want to punish her by playing games with her mind
You shouldn't want to play mind games with your girlfriend. It sounds like you should just break up with her and move on if you don't even like her.