I guess she might not much like vampire stories if they're no longer escapism or worse are now insulting. Vampires haven't been good guys in fiction until modern days. She doesn't seem to like being called a vampire, but then she's happy to call Tatsumi and company werewolves based on them being common in werewolf stories, isn't she? In the two vampire canons I know of (but haven't personally read--Twilight and Parasol Protectorate, a popular series with my RP group) vampires and werewolves are enemies, as far as I've been told.

I suspect Ono didn't go for symbols only mattering when you believe in them since a major theme for Seishin's arc is the type of 'faith' that's considerably more personal and thus less based on rituals and symbols. Too much focus on symbols can undermine that, while just a little bit of it focuses on how ostracized the Shiki feel by it being excluded from or running counter to the natural order. They can't go along with the ordered faiths that hold societies together any more than Seishin can (for personal reasons on his part).