YTA... kind of... while I disagree with the today's day and age of "participation trophy" encouragement, having the knowledge of your GFs lesser skills at the game yet still going "try hard" on her makes you a bit of an asshole. Typically when my GF and I start playing a game together i try a different character/building strategy than I normally would when playing alone. I do this because my GF isnt as into video games as I am but I like playing with her which sometimes forces me to either try learning a new character/build or playing a lot more lackadaisical. Now I say kind of because your GF should also understand that sometimes playing with someone who has greater knowledge of the mechanics or the game tends to mean they progress quicker/shell out higher damage and she should take initiative to learn and try to increase her skill at the game. But I still stand by what I said previously in that I recommend not going super try-hard when playing with your GF