I don't know if we know yet what we can call Darla. What we do know is that SHIELD allowed her into Potts Tower and didn't dust her, shove her into a cage, or whatever it is they do with those things that are coming through that are not safe - and clearly they're doing something because occasionally some of them get through and escape or we wouldn't be dealing with vampire nests. To me the fact that she's here does say something, and right now we're operating on no information.
I think you can believe Angel, and Spike also - although I can't believe I'm saying that - when they say they don't want her to hurt anyone. It helps no one if that happens, not her, not Connor, not Angel, and certainly not the person she injures.
I don't believe we should be cavalier and say 'she's safe', but I do believe we should try to be sure she isn't before we crucify her. We've all done things we regr