I'm going to break up with my girlfriend and kick her out of my apartment
Why would you want to break off your relationship with your girlfriend and kick her out?
Because she could not pay her share of the rent
You are making money the main focus in your relationship and this will damaging to you guys. Money is not more important than maintaining the relationship with your girlfriend. She may be going through a financial hardship, you should be more understanding.
Okay, I'm just going to not talk to her when I get home.
I'm glad that you decided not to kick her out of your apartment but again you're still upset about her not paying the rent. Talk to her and give some time. I'm sure she'll be grateful if you are empathetic to her situation.