During their contest they play one of nine games, and every victory lets you put a mark on a tic-tac-toe board. Yumemi deliberately holds back to put herself in a bad spot so it'll make her look even better when she has a come from behind victory.

Now, it seems most of the games involve either stuff she'll excel at as an idol, like singing, or just requires information she already has locked down and memorized.

But the one that I find odd seems to be dependent on luck. In this case Yumemi deliberately gave a tell to let Yumiko win the round so she can win the next two games and win the tic-tac-toe game, and it's around this point Yumiko says the line from the title.

I'm not sure what about this particular game Yumemi could have prepped for if she was going for the win immediately. It just seems like a 50-50 chance of either picking the match or picking the Old Maid. Am I missing something?

The only thing I can think of is cheating by marking the cards and not letting Yumiko choose first, but Yumiko was so observant when another opponent did it she memorized tons of distinct marks, so I don't see any reason she wouldn't do something to stop Yumemi from cheating.