I feel like she pulled the best anti-conspiracy card with Ayu's parents, tbh: "The moon landing was faked!" "Huh, you believe the moon is real?"
When faced with ridiculousness, respond with equal or greater ridicule. She was facing Ayu's parents with that spirit: confronting the ridiculous (homophobia) with even greater ridicule (overt display of money talks). That was why she could so easily bring up the topic of hiring an assassin and stuff—she was not taking Ayu's parents seriously to begin with, because she knows they won't change their mind.
Might as well push them to the brink to let Ayu go by their own choice, and she did exactly that.
Also I'm kind of glad the author chose the ending where Ayu walked out, even if she was disowned. It's a rather grounded situation for a lot of homosexual people coming out to homophobic families; at least here Ayu entirely cut ties from her family rather than forcing the tone-deaf Japanese sentiment of 'family is family in the end of the day'. A manga that cuts off abusive relationships is good in my books.
All in all, a lot of suspension of disbelief had to be gathered to read this through, and the ending was tonally odd, but otherwise a fun ride. Thank you for translating this to the end.