[[SPOILERS AHEAD]]
To all; say what you want about Cass, although she is not my favorite I wont deny that she is certainly a ride-or-die chick and probably sees MC like herself too. I mean she knew and said that coup's success depends on MC and so it did. She fucked up without MC, she knew she was going to fuck up without MC. Thing bothering me is that her foolishness reached to point where she convinced herself MC wants the exactly the same things as herself and when turned down she either gets herself killed instantly in self-pity (aka suicide) or initiate her half-baked plan which may be called her prolonged suicide. The coup was in motion way before the wedding maybe even before MC came to palace... This confirms she really believed MC would want to join her. She hoped that MC is still the mischevous kid she knew and hoped that exile, humiliation and all the other things made him bitter or better yet vengeful like herself; because this is what she became after all that.
Behind that pragmatist and physco mask; she is very lonely, not alone mind you. Yeah, she has her aunt and her uncle or whatever... They only use her for their ends, for their revenge. All you simps, simping in harmony, praising her: Queen this, Queen that blabla... ignoring the fact that she is the one who broke the family up. Caused the exile of MC therefore made Cass isolate herself, made Elin go to the Tower. In addition to these, she may have been the mother figure for Cass but no, she choose to antogonize her. No doubt Queen has her own agenda in favor of MC but come to think of it, did she ever asked what MC wants? Quite the contrary, she is being rather pushy about whole regency and succession thing. Add to this: although she didn't make any moves yet, she is certainly the one who set the events in motion in the past. All these reminded me of a line in the Dune, a line about Jessica.
“My mother is my enemy. She does not know it, but she is. She is bringing the jihad. She bore me; she trained me. She is my enemy.”
―Frank Herbert, Dune
Hey, I may exaggerating things lads, feel free to give haha reaction or better yet bully me.