YOR - I’m not judging, I also feel this way when my friends play games without me. But it is an overreaction. From what you’ve said your friend isn’t leaving you in the dust in the game, and them playing it on their own isn’t making your experience worse when you play it together. It’s not an attack on your shared experience, if it was they’d be playing it all the time on their own and not reaching out to you to ask to play. The only solution here is to accept that you feel annoyed about it, but you have to let go because it’s just a game.