Well, sort of. Actually Rhea killed her husband, Lar Gand, on Supergirl Season 2 Episode 17, but honestly, who didn't see that coming?
Rhea is crazy, and she's clearly willing to do anything to get her son back.
Well, I guess it is safe to say Mon-El is no longer the Prince of Daxam. Daddy's dead, so that makes him the king. Not that he has any interest in claiming his throne.
So far Rhea's unwilling to kill Mon-El, despite the fact that he is against her. It begs the question: why does she care so much?
Does she really, truly love him and this is her twisted way of showing it? Or is there another motive behind her insistence he returns to Daxam?
I understand that Rhea wants to save her home planet and get things back to the way they were, but why can't she do that herself?