>>54813763Where are they meeting, her hometurf, Circhester, Wyndon? She's obviously into music, maybe they meet at an underground concert and hit it off in there. She was raised in a shithole by a gang-leader rockstar, she's a tough nut: maybe the MC's getting mugged in an alley and she steps in to save him, and maybe she even knows the muggers personally. Maybe they're spectating a match together instead of having a battle, and her Morpeko steals the MC's food or runs off with his hat. Maybe one of her own pokemon is injured and they meet in the hospital and have a heart-to-heart or something.
Whatever, there's a lot you could do. There should probably be some purpose behind it though. What makes Marnie and the MC fit, what traits does Marnie have that the MC is lacking in that you could highlight in their first interaction? What sort of impression does the MC have of her after their first meeting: does he admire her, hate her, fall in love with her, and how does that affect the story moving forward? I would try experimenting with a bunch of different scenarios and seeing which one fits best.