How do you tactfully tell someone to go to hell?

Long story short my boyfriends ex sent his sexy messages and I was way too polite when I asked her to refrain from such topics and she told me she would talk anyway she wanted with anyone she wanted. last night she told him she loves him and not in the "we're just friends" way. I'm done playing little miss nice nice I don't mind them being friends, but I do mind when someone speaks to anyone else's boyfriend that way especially when they supposedly have one of there own. I need help being nice but not so polite without being overly rude
How do you tactfully tell someone to go to hell?
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