Cirno's hand is not legal. You're supposed to have 4 Ones and 3 Nines, or 3 Ones and 4 Nines. But she has 4 of both, so she doesn't have a pair. It's such a rare hand that making such a mistake is the height of stupidity.
To win in Mah-Jongg, one needs four sets of three and one pair. Nine Gates is either 111/123/456/789-99 or 123/456/789/999-11. An easier way of seeing this: Any winning hand has fourteen tiles, whereas ⑨-chan has fifteen. ((Side note: It's not hard to pick up extra tiles in the beginning of the game. However, it IS hard NOT to notice that you have extra, and there is no way to legally fix this problem, so one usually doesn't even try to form sets after noticing.))
As for China's expression, only the player who throws out the tile that causes an opponent to win must pay, so no one else really cares, and Nine Gates is worth a LOT of money. ((Side note: If you pick up the tile yourself, everyone must pay.))
In addition, it is bad superstition to falsely call that you won.
What irovax said is mostly correct, however, those are not the only arrangements for the 9 gates.
9 Gates requires you to have 111-2-3-4-5-6-7-8-999 and one more tile of the same suit, so the hand satisfies the conditions of having 4 sets and a pair. For instance:
111-(1)23-456-789-99 111-2(2)-345-678-999 11-123-(3)45-678-999 111-234-(4)56-789-99 and so on.
This still does not completely explain Cirno's hand, however... Until you take into account the fact that you can call 4 of a kind, and when you do so, you draw an extra tile, so that your final hand is 15 tiles. So, this means Cirno's hand is... still illegal, because she has a second set of 4, which means her hand should be *16* tiles. So in order to have a legal hand, she needs one more tile... There are only 4 of each tile in a set, so, 1 or 9 is out of the question, and, looking at what her hand would be--
A note- when you call four of a kind, you are forced to continue with that four of a kind in your hand in order to draw that extra tile. So, any hand mentioned above does NOT work if it does not contain BOTH 1111 and 9999... so her hand only works if she just called a 2 or 8 from China.
China should already know how this game works and not rely on me to the ⑨s of the world.
