I don't feel like she is, I mean she seems less and less evil the more the season goes on. First we learn that she was turned into a cannibal by Seline (I don't care what you say Seline is clearly the definition of a psychopath she murdered and ate people as a child) I mean I think Seline or Cade will be the big bad of the season. I mean clearly Seline is still clearly Cade's fan girl and that scene where she kills Georgie is in my opinion proof she hasn't really changed if only because she clearly (from my perspective) enjoyed killing Georgie.
Also I've seen the preview for the next episode and it looks like Damon is going to flip out when he sees Sybil in a similar dress to something that Elena once wore but it seems like this wasn't intentional on Sybil's part. I think what's interesting about Sybil is that it's like she's slowly becoming more human first she has that moment when she cries in front of Stefan, then she opens up to Damon about how nobody wants to die what's interesting is it seemed like Sybil felt sorry for the people they were about to kill, then there is how she talked to Caroline about a place to live in Mystic Falls, finally and I find this the weirdest part she pretended to be a teacher even though she just needed the kids for leverage.
I feel like Sybil isn't a Katherine but more like a Rebekah Mikaelson because she keeps reminding me more and more of Rebekah than Katherine as the season goes on. it makes me think about the line in an earlier episode "Two siblings one trying to live like a monk." maybe that's who she is in he Siren sibling dynamic.
Maybe Sybil tries living a normal life then Seline ruins it and Sybil spirals and doesn't something bad and Seline berates her for it. Basically what I'm saying is