Though she did seem Tsundere like, she also seems to dislike Mamiko very much. Can't wait for the jealousy arc to transpire so Nobu would soon realize her own feelings.
I like that they are both pretty much putting on an act at school so their persona matches their appearance even though it looks like the "Princess" is more of an abrupt/tsundere type and the "Prince" is more of a princess with a bit of a reckless streak at heart.