You assumed that she became attracted to men because of the memories rather than it being her natural state.
The MC so far hasn't declared that she need to turn gay to defy destiny. She merely refused to obey destiny.
Anyway, the MC being straight or gay is neither necessary nor relevant to...
Has she?
The scientific use empirical data to test and justify hypotheses. And as far as empirical data go, there have been no case of extra dimensional fans/readers/players possessing a protagonist from our (real) world.
The "game" is a story element. But the story itself (that we the audience are reading) is Seinen.
Also, from a narrative standpoint, Aria set out specifically to not follow game story. She was disgusted by the game story. To make her just as "thirsty for cock" as the fujoshi contradicts the...
Why would you want to subvert expectation for the sake of subverting expectation? To be "different"?
Many readers expect fantasy to be fantasy. And for most of the time, it is better to keep being that way.
Well, this is shounen, not shoujo. Such a plot either wouldn't happen or would be rendered irrelevant. Besides, the more the guys otome male leads fall for the fake one, the more it benefits the MC's goal. To vie for some male's attention is beneath Aria's person.
Well, I don't know how it works in Burgerland or Nihon Koku but here's in my country, early marriages between kids are frown upon. Such practices are outdated customs reserved for the under-educated in far-off under-developed places.