For anyone unaware, this is because Min Min just won a Party Crash (basically ARMS splatfests) that was a tournament between every ARMS character that took place over the last 8 or so months. She won the finals versus Ninjara, the only character she'd lost a Party Crash to in the past, and also ended Ninjara's perfect victory streak.

In short, she's now confirmed as ARMS Best Girl.

plot twist: this was all done to decide which ARMS character gets added to Smash

(they were confident Spring Man and Ribbon Girl would not win)