Actually, this is not yet a closing hand. There's only 13 tiles here, whereas a closing hand requires 14. Best guess is she is declaring a riichi for Kokushi Musou.
...but one does not declare riichi with the 5000 (or was it the 10000?) stick! =))
It's probably because one of her signature moves in the game is called "Thirteen Orphans". I know nothing about Mahjong, but I'm assuming it's a reference to this hand.
It is a reference, it is of the 7 ultimate hands in mahjong. Too bad they didn't show the last three tiles clearly and Astana's right it's not a closing hand, she needs one more wind tile or dragon? tile to complete the hand.