The vampires can see the other vampires. They can also see the vampires who gave up their teeth for hammers and silver spikes. They will go for the jugular. They -have- to go for it. They are psychotically paranoid.
Years of overwhelming, innocence-robbing, violent incest made them that way. They see their vampire characters as a proper and acceptable means of surviving a world full of unfair persecution. So they must persecute first.
There is only one possible combination of emotions: obsessive hatred of anyone who shows them romantic attention, and sadistic delight in shredding that person (if they can).
"Don't think for one second that this is the end of us, Bobby."
The borderline can say this with complete certainty because she has learned (and rehearsed and rehearsed and rehearsed) her "others" for so long to protect herself from the terror she experienced that she truly and totally believes she is not who she is.
Fortunately, most are not so sinister as Nicole here, but just to be safe, it's rarely a great idea to let them know you can see them unless you really -are- a police detective.