Seline

I became a bit confused by how the sirens' mind control worked after ''We Have History Together'' and throughout the remainder of their appearance. Despite it appearing beforehand that Sybil and Seline had no trouble "sirening" vampires as old as Damon, Stefan, and Enzo, why was it that Sybil seemed so unassertive with Caroline in the episode when prior she seemed so fearless and confident. I was confused why she had to resort to manipulation and trickery to get Caroline to do what she wanted, as opposed to just mind controlling her. A few episodes later Bonnie expressed worry Sybil would mess with her and Caroline's minds should they release her from her confinement, implying she should have had no issues mind controlling them. Was it that Sybil, unlike Seline (or so it seemed), needed to come into physical contact with those she wanted to control? Did she have some sort of personal preference towards controlling men? Or, did no longer serving Cade directly weaken her mental powers? I don't know if there was something I missed or not when watching the season.

I saw some old speculations and some fans say because of her meanness, but in the last few eps she showed remorse for Damon when she entered his mind or when she apologized to Seline.