<human>: I'll get to the short of it. Her ex of two relationships ago is texting her late night for sexual favors. They're friends and have been friends for a while now. They share the same circle of friends.

So, It started with a couple of times when we first started dating, she declined and told him that she was seeing me. But recently, this guy has become more of a pest. With texts coming just about every week. She always tells me and shows me when they come. 

How do I go about telling her that she needs to be stern with this dude and tell him to stop without A: Looking like a dick and trying to dictate her life B: being insecure about another guy?

I know she would never cheat on me (this guy cheated on her as to why the relationship ended), our sex life is great, she loves me. It's just this guy being annoying. 

I've met him, we're on a mutual level and he respects our relationship when he's around, of course. He doesn't know I know, and I still maintain my cool, but I'm worried I'm going to pop off on him about it when it's not my place to say, but hers.

Can you succinctly summarize the text in 1-3 sentences?
<bot>: GF's ex is texting her for sexual favors. It's getting annoying. How do I ask her to say something to him without looking like I'm insecure or trying to tell her how to live her life?