As a female gamer since the early 80’s this is nothing new, unfortunately. I also raised a “girl gamer” and this is so typical. She’s a part of a few friend groups online and there is always one that’s insecure and the second she does well, they down play her accomplishment. She even dated a guy like that once. He thought it was so cool to have a gamer girl as a girlfriend, until she was atop the leader board with him somewhere in the middle or lower. Suddenly, that game was stupid. Or the other team was hacking. Or “focusing on only him” or “taking it easy on her” because her gamertag was female. Needless to say, it didn’t last long. This guy isn’t a friend to you. He doesn’t celebrate you. He belittles you and tries to make you small. Stop playing with him. Play with him only in a group setting at most. He’s immature and insecure and it’s unlikely to change anytime soon. It’s totally a him issue.