Girlfriend and ex-boyfriend are dating. Should we break up?

You shouldn't break up with her like this. You should try to communicate with her first and know the specific situation before deciding whether to break up.

You should explain your feelings directly to her. I suggest you ask her directly why you two are still in contact. If her answer is: we are friends and send messages occasionally, it's nothing. Don't be so narrow-minded

Then tell your girlfriend: when two people are together, they should get along well. What am I if you contact your ex-boyfriend like this? Have you considered my feelings? You think it's nothing, but it's a taboo in my heart. If we can still be honest together, please don't contact him again. If you think it's nothing and never consider my feelings, let's break up.

After you talk about your relationship, it depends on her state. If she looks cold, you'd better not talk to her more, because she really doesn't put you in a very important position. In her mind, her ex-boyfriend is more important than you. So, in this case, you two can choose to break up.

But if she realizes her mistake, apologizes to you and promises never to contact her ex-boyfriend again, it means that she still cares about you, she will consider your feelings and emotions, and she also hopes that your relationship will last for a long time. This also shows that there are some inevitable reasons for her contact with her ex-boyfriend. In this case, you shouldn't cling to this problem. You should give your girlfriend a step down and take the opportunity to express your love for her, so that your feelings will get better.