Although you don't interact much with the Vallyries in a casual environment due to your job, you have never turned down an invitation from them from time to time; a break can't hurt you.
Even though many girls warned you that playing against Bronya was a sure way to lose... there you were, giving her the beating of her life in her own HOMU-station in a fighting game that you "never" played before.
"Even though I'm trying to analyze you, I can't figure out how you perfectly used a tier S character without having played before."
Bronya's poker face was the usual one when weird things happen; she didn't want to admit that it was silly to underestimate your ability to play video games, although she was still having fun... in the background, without saying anything.