Open relationship? She'd get a slap across the face and if she talks back after that she gets another backhander in the gob.
"Bitch, I'll keep fucking other girls and you better have my dinner ready when I come home after a long day of going balls deep in the neighbours daughter or I'll fucking break your jaw into 6 pieces, you got that, Whore?"
Treat 'em mean keep 'em fucking keen
edit: on a more serious note...if the words "open relationship" or "seeing other people" or anything of the sort cropped up in a conversation, I'd have her by the hair dragging her down the hallway to the door before she finished the sentence