The only way I'd ever be willing to somewhat accept this type of plotline, which could admittedly fit with the themes of the series, is if that Lily girl had actually loved Imu but fell out of love with him after he'd went off the rails with his cold-blooded plans for the world and ended up creating Amazon Lily because he made her develop disdain for men, until she met Joyboy, fell in love with him and joined his fight against Imu, whom she still cared for in a way.