YTA

She's trying to get into an activity that you're into so she can enjoy it with you. You did a great job ensuring that that won't continue to happen. Not only did you make the game not fun (it's never really fun being destroyed and feeling like there's nothing you can do about it).

Also, it's a game you've played extensively and one she's learning. If my college soccer team was somehow beating Liverpool in a friendly scrimmage, we'd talk trash about it. We know they're not really trying their hardest, they know they're not really trying their hardest, but it's still a funny outcome given the two teams. If they suddenly tried their hardest, it wouldn't really be a very fun or entertaining or productive scrimmage for anyone. It would just be one team watching the other team repeatedly score at will. Who gets anything out of that? The game would obviously stop being fun. Which is fine I guess, but this is your girlfriend who you presumably care about, and why would you want that to be the end result of playing together? Oh man, I'm going to do everything I can to get her not to participate in this hobby.

But what really made you the asshole was the, "is that supposed to be a punishment for me lmao?" Yeah, fuck her for trying to find a fun mutual activity for the two of you to do together.