Most Helpful Girl
Simple: move out and establish yourself as an individual man that your mother can't control. When she insults a partner: you stand up for that partner. If your mom can't understand that, then you get rid of mom. This is a problem that causes a lot of failed relationships and divorces. You nip it in the bud now, and if that doesn't work, you cut ties with the controlling parent.
Most Helpful Guy
You need to get away from living with your mom, then tell her that if she wants to have a place in your life, she must stop acting like a jealous girlfriend.