I'm mad at my girlfriend after she chose to party with our friends while I was sick at home
Why are you mad at your girlfriend for going out?
I'm tired of doing everything for her. She never thanks me for anything so she doesn't deserve a night out.
You should not be upset with your girlfriend over this. It is not okay to get angry over her going out for a little relaxation. If you have issues with her not helping around the house talk it out with her.
She will get what's coming to her. I'm thinking of leaving her too.
Being pissed about helping around the house and going out with friends is a really minor thing and you should not get all worked up about this stuff. Let go of the trivial things in your relationship and focus on the important stuff.