Crazy exes.

How do you guys deal with your partners crazy ex? Me and my fiance have been together for 3 years now and we are expecting our first child together. He has a daughter from his previous relationship we have his daughter 5 days of the week and the other 2 she is with her mother, so unfortunately his ex is still around. Every 6 months or so she decides to start acting crazy and I am tired of it. Just over this past week she has decided to start messaging my fiance inappropriate things and I'm just having a hard time with it. He always tells her to stop and to respect his relationship and how he only wants to discuss their child and nothing else but she continues to do it. Does anyone else have to go through this?