Does his girl belong to the streets?! She doesn’t put a stop to her flirty coworker.

My girlfriend has a coworker who flirts with her nonstop. He’s always asking her out to lunch and sending her texts. She says he’s innocent and harmless but it bothers me that she lets it happen. She tells me everything and we laugh about it but it bothers me that she doesn’t put a stop to it. I always joke about showing up to her work and telling him myself but she begs me not to. He knows I exist but he is still hits in her everyday. Does she belong to the streets for not telling him to stop and that he doesn’t have a chance? I’m starting to get irritated by this whole thing. Help me out crew!