But, you ask, if this is a game, what do you gain or what does she lose if you do cum?
"Well, here's what I thought would get you motivated:"
"How about each time you cum, when we are playing this variation, then you get an extra bead the following week."
That sounds like a double bonus to you. You affirm that in that case you'll want to cum as much as possible.
Of course, you can see that she'll also try to prevent that. But it sounds good, and your opponent certainly looks good!