After defeating her in the Nighthold, for the last time it is shown that Elisande didn't hate Thalyssra or the Nightfallen, she simply disagreed with them on the way of how it is best to handle the Legion situation – and that disagreement caused a civil war while they were facing such a dire threat. She didn't sympathize with the Legion, she agreed on having them because it needed to be done in order to not be annihilated by them. In a perfect scenario Elisande would have wanted to defeat the Legion, not to let them into Suramar, and not to send Thalyssra and everyone else into exile, but she didn't believe that was possible – that's why she didn't allow Thalyssra or anyone else oppose her while accepting the Legion's offer and send Melandrus to assassinate her.
It really made me feel more pity rather than anger for Elisande for her being put into such a difficult position. She is not a generic character that screams "I AM EVIL FEAR ME BLAHABLAH", her motivations are simple and she is facing certain dilemmas, her decisions have their consequences, but in the end she is willing to admit that she might have been wrong and after her defeat she wishes her best upon the heroes – because all she cared all along was Suramar and the Nightborne.