a c t i o n » Oh. [ Not entirely a surprise as he already expected he would have told her about Stefan. After all, there's no point in keeping it a big secret. Sooner or later she would have found out why Stefan did what he did and Elena deserved to know.
Right now more than ever though, he felt that Stefan's little sacrifice had been a complete waste (not that Damon thought it had been a good idea in the first place as he didn't need to be saved), considering the whole being stuck in prison thing.
As for any attempt to gain Elena's affections with Stefan out of the picture...