Baby mama drama

My husband and I never fight but when we do have disagreements it's always about his ex which is his daughters mom. I can't stand her. She's always in our business. Always contacting my husband for things that aren't about their daughter. She's in a bad relationship and isn't happy and sees that we are and she hates it. She hates me. I don't know why I let her get to me. Anyone that has a similar problem can help me???