This definitely tells me that either Rowling didn't think of Alice as an auror at this point (maybe it had been an early concept, then she forgot, then remembered to add it later?) or else Dumbledore is deliberately emphasizing Frank here. For God knows what reason.

It's odd of Rowling to change her mind over something so relatively inconsequential (or maybe not, with her continuity standards) between books four and five. But making a point of obfuscation seems very odd as well. :p