What do you do next when your partner refuses to break up?

What do you do next when your partner refuses to break up?

“My girlfriend and I were dating for a year and over the weekend I told her I wanted to break up. She responded that she doesn’t believe me and that she thinks it’s just a phase. A few days later she came over to my place like nothing ever happened. I told her again and she still doesn’t accept it.
How can I get her to realize this is real?”