You have to do it like boiling a frog.
First month: tell her you like sports. "Hi honey, no I can't make it tonight, I really want to watch the game."
3rd month: "Wow, my friend Jerome is going to win a lot on this game, the Dodgers are killing it!" Gauge her response. If she sneers, you have to slow the rest of this timeline down. If she goes "Really? He wins money on sports?", you're good on this pace.
4th month (while watching game in front of her): "I really hope the Heat don't lose by too much, if so I get a free $50." If she asks how, explain you got a free play for nothing as a trial from a sports betting website. Gauge her reaction.
6th month: Tell her you got a nickel on the game, that it all came from free money you built up from one of those freeplays. Make it clear you're just playing with house money. This desensitizes her to the idea, no downside, only upside.
9th month: you can fill out your parlay cards in front of her Sunday morning and tell her what youll have for dinner depends on Patrick Mahomes' passing yards. It's just your little gambling hobby. Tee hee hee.
It takes long but it WILL pay off.
After a year, you can swear at the TV in front of her and be openly in a bad mood if you lose. If she expresses concern about how much you're losing, ask her how much her last fukkin purse cost YOU BITCH!
After two years you can siphon money from her bank account and tell her it was for medication and you don't want to talk about it... YOU BITCH!
After three years you can ask her to ask her family on your behalf to help pay off gambling debts.
Soon after that its time to find a new broad to repeat the process. Sports bars can make this process go a lot faster but in my experience broads who go to sports bars have family with their own gambling problems.