Although this is a scenario I'd like to roleplay with someone I'm happy to adjust aspects of it if you like the idea of it being a little different in some way.

During the time you were living with my neighbour we got to know each other as we bumped into each other a lot in the corridor of the apartment block. You also got to hear through the walls if I brought a girl home and, although you'd never have said anything to your boyfriend, you had to admit it sounded like my hook-ups were enjoying themselves. It wasn't too tricky for you to pick up that I was jealous of your guy being with you. The way I would look at you when you were with him but flirted with you when he wasn't around made it pretty obvious. But this month you discovered he had cheated on you multiple times and you left him last week after an argument that the entire block could overhear, where you called him a disloyal little shit and told him he should go fuck that tart of his because he's never getting any more from you.

When you go back to pick up some possessions you discover he has a girl with him in the flat the two of you used to share. His behaviour leaves you in an angry and emotional state and you come to my door "to talk things through". I open a bottle of wine as we talk and we end up getting drunk together. I spot my chance to finally hook up with you and, knowing the walls are thin, you see your opportunity to make your ex jealous. By the time the evening is over we've both made a mess of my apartment and each other as we fuck hard in multiple positions and multiple rooms of the flat.