Yes, and she will do it for the power and to spite her sister. It will not occur to her for a little bit that Adam is missing also because she will be so focused on Ciara. 

I would be okay with that! I don't really care who he kills as long as it is not Ciara. He could pick their daughter because she is strong in power and looks similar to Ciara in hair color?

I think doing it a little after he leaves. I was thinking he would disappear on her and we would wait long enough for it to sink in and for Ciara to realize what is happening. Then I was thinking she would reach out to him and ask for him to come meet her to explain himself and it would just go down hill from there.