Lord_Enki said: Being a zombie, the seal may be a reanimation slip, thus causing her to die. Or, it may be a power sealant, not unlike Rumia's.
Being a jiang-shi, it is most likely that it is a reanimation slip, though the power seal is still possible (Hsien-Ko, a similar character, has a seal to keep her power under control. The Jiang-Shi boss in Castlevania: OoE is also defeated by slapping a seal on his face. This seal is removed if you hit him afterward, causing the fight to start all over again).
It reminded me more of Nitori at first too. It's pretty justified. The shape of her hat is more similar to Nitori's than Meiling's. The star is what tipped everybody off toward Meiling rather than Nitori.