How can I make things right with my mom and just move past this whole thing?

My mom and my ex have never really liked each other, and they have their reasons. On my Facebook status they were joking around and getting smart with each other. And my mom is a cop. And my ex made some not so nice comments about cops. And things got taken too far. Now she’s telling me to delete him and not talk to him, but I kinda like him and I think he likes ne too. And I REALLY don’t want to do that. How can I get her to calm down about the whole thing? Please help me. I’m very upset.