Her marriage to Killian meant she could no longer be on Blackwell's side. She had two kingdoms to care for and though she was Blackwell royalty, she would not place this kingdom higher than the north. In her new life as queen of the north, there will be people she cares for and it would be a big betrayal if she allowed Fraser or anyone else to harm them.
Clearly, Fraser did not get the notice to grow up and not be so childish.
Fraser made a mental note to remember what Amelia chose. Not like he wanted her to be on his side anyway. If he were to attack the north as a precaution to ensure they do not attack this castle again, he would prefer for Amelia to die there. After their grandmother died, he would be the only Blackwell left. If he was generous enough, his mother could change back her last name even though she is married.
