Half hour video explaining the whole thing.
TLDW: Female character is a womanizer/highly attracted to females (although apparently not a lesbian), a trait she comically inherited from her womanizing father, to the point where she can't even stop herself from hitting on her own mother.
She expresses her dismay over her predicament to the male protagonist.
At their next meeting, it's revealed that the protagonist drugged the female character, without telling her, in an attempt to help fix her problem. Now she sees men/women genderswapped. The protagonist offers himself up as "training" so she can work out her issues on a test dummy. She's not at all upset by the non-consensual drugging. The training doesn't work, and she runs off to go play with her new ability.
Later, she accepts the protagonist's marriage proposal, and points to the drugging incident as the point where she fell in love with him. He's offended that she fell in love with the female version of him, but she says that while his attractive female-self was a factor, she loves his male-self and is grateful for his attempt at being helpful.