If she wanted a spy, she should go for someone like Catherine.
Even the suggestion of getting to marry Brian, especially if it's instead of or ahead of Hannah, would be *extremely* tempting for her. (even being 2nd wife would probably tempt her given her family's circumstances).
That doesn't make any sense. Firstly I only mentioned Akatsuki because of how the other person randomly chose Lucy and Victoria. Any random commoner would do as a plant. Lucy and Victoria are ride or die for MC, they would never betray him.
Catherine would gain absolutely nothing by either marrying Brian instead of MC, or by marrying MC with an eye towards taking down his Family.
Her whole thing is wanting to marry a family head.
Marrying Brian would be an absolute last resort, she knows the type of person he is, and she's seen how MC treats his girls, she wants the life MC can provide. So no marrying Brian.
Helping to destroy MCs Family would ruin her life. Say he succeeded in helping have MC exiled like his grandfather, she's the only one how would pay the price. The core four girls would happily leave with him. So say she was to get a divorce in whatever deal made her help destroy MC, and say she changed her mind on Family Divorce, if it became known that she was involved, there's no way in hell she'd get to marry another Family Head after that. She doesn't want to marry down into any branch families. So again, helping to destroy MCs Family would ruin her life, there'd be zero benefit.
The only type of person I can see working, would be a commoner, who desperately needs something done, that only a specific Family can do. Say something than can save a loved ones life.
I don't remember that being said. I might be wrong, but where did you see that?
I don't remember where, but assuming I'm right, it would have been fairly early on in the game.