I honestly believe it is because all she cares about his the trio, and anyone she feels gets in their way has to go
All I can say is if Kevin Williamson was still directing, Kol would have lived ALOT longer. He knows how to stretch a characters story out.
I believe she finds boring people more interesting I guess then the ones that the fans tend to like. Ex-Kol or Finn.
I would have liked Kol or Finn around a little longer but that is just my opinion, there are also some other favorites of mine that I would have liked around a little longer.
What do you think?