There are 2 ways I would suggest to go about it.
Either,
Make it like the wrestling or the volleyball game, and have all the fights be scripted with different options on how to react.
It would be easy to balance and give players some nice pictures to look at during the fights, so even if you plan to lose it's worth doing the fights.
But you would lose the game aspect of the fighting system and it would be even more renders that needs to be made.
Or,
Make it more like rock, paper, scissors, and give everyone and all attacks an "element", and damage gets impacted based on who you are fighting and what move was used last (if that's even possible in RPGM).
My suggestion for that would be:
Grapple, dealing medium or continues damage while restricting what moves the opponent can use, grabbing arms, giving wedgies or stripping opponents. Used by people like Jess and the wrestlers.
V
Physical, High damage moves like pulling hair, slapping or knee strikes. Used by people like Poppy and older bad girls.
V
Vocal, low damage while debuffing opponent, buffing or healing yourself/allies. Used by people like Stacey and the popular girls.
V
Grapple, here to show what Vocal beats.
Have Missy start as natural "element" but allow items to chance her state.
And to make it feel even more worth it to fight, you could allow attacks to be unlocked as you beat opponents or during scenes like Jess teaching you wrestling.
It would feel more tactical and be nice story wise to have the girls move set based on their personalities.
But it would be a whole lot of work for a system very few players even use.
