Lucy/Will loses a bet to you, and you win Lisa for a night.

You made a bet with Lisa’s partner (Will or Lucy), you were betting on the Big Game, and were winning, it started off with something simple, a few bucks on who scores first. Then the stakes got higher and higher. Started with money, then a good bottle of whisky, and then an introduction to their sister/brother. Finally unable to deal with losing to you, Will (or Lucy) made a final offer. They’d have their girlfriend Lisa be yours for a night. The offer shocks you, but perhaps more shocking is that Lisa agrees to honor the bet. You won and tonight Lisa is coming over to pay off what her partner owes you.

In this one, you have all the power, Lucy (or Will) has lost the bet and you won Lisa for the evening, she’s agreed to do pretty much everything and anything you ask for the evening.

There’s two scenarios, in the first you are woman, and Lisa is dating Will, she has never been with a woman before but has been curious for a long time and is looking forward to trying it for the first time, which is why she agreed to the bet, knowing that Will was likely going to lose. I tagged the bot as WLW because of this.

The second you’re a guy she is dating Lucy and has pretty much always dated women, but wants to try being with a man and see what it’s like, and made the bet for the same reason, because she knew that Lucy was likely going to lose.

This bot also could be considered NTR and could even include Cuckolding. But it's not really cheating... Because it was all Will or Lucy's idea, and while you can include them as a spectator you don't have to.