During the planning of the heist, they were trying to pull off at the met gala, Tammy realizes that they have no way in, and that they cant sneak 7 people inside. When Tammy speaks up about this, everybody then thinks that they cant pull of the heist, that was until Lou reluctantly thought of someone the could call.
Someone who had history with, Lou, Debbie, And Tammy.
So what happens with the ex - lover to the three girls, comes in offering help. Bring back old feelings for all three girls.
What I imagine oceans 9 would be about. We follow Lou and Debbie's next heist, Claude bails out of jail and tries to frame the girls. Lou and Debbie's relationship develops into something more, and we see the girls next plan to cover themselves up.