Mortal Instruments Fans: Question about the circle?

I think it was because he made her really trust him, and she almost died at the Uprising, which would have left her son, Alec without a mother. He is also the reason why she cannot live in Idris, because she joined the Circle and participated (although briefly) in the Uprising. They did not date. Also, it could be because of what he did to Jace, who she grew to love as a son.

I also have not read them in a while, but I hope my musings help :)

in the circle was Jocelyn (but she left because valentine was turning into something she was scared of) valentine (Jocelyn then husband now ex-husband), Maryse lightwood, Rober lightwood, Lucian Garymark (kicked out by valentine after being turned into a werwolf and now goes by luke garroway),and Micheal Wayland and I'm pretty sure they didnt date i believe he broke her heart because he became something that nobody thought he would be a monster