Well I was thinking because Katherine is a vampire and she's lived in the town twice now in the last few decades. Either she's really good at avoiding werewolves or they've never noticed her... o.o
Oh, I see, and Too true! Maybe... Well, it might be a little out there, but since she's been so frequent in the town, and also considering she's already sixteen centuries plus; maybe she's figured out a way to cover her scent with something, as well as avoiding any unnecessary contact, she might have been able to fly under their radar that way? Or, relate it to her ability in a way would be a good; like when ever she morphs into any animal, her vampire scent changes perhaps? Food for thought.