MIL ISSUES

So my mother in law has always had it out for me, she’s always been jealous that I’m the number one woman in my husbands life now and she no longer is. She texts him like a psycho girlfriend that won’t go away. She will try to text him all day every day. She texts him on the dot when he wakes up to tell him to have a good day at work, and texts him on the dot of getting out of work asking how it was. Every. Single. Day. Sometimes when he doesn’t text back right away she will call him. He’s been trying to ignore her but for the most part he doesn’t see anything wrong with it, I for one find out very obsessive and weird as hell. It’s weirding me out so much it’s starting to put a damper on our marriage. Which is what his moms going for. What are some things he can tell her to make her back off and not try so hard?