You're kinda making something out of nothing. Camilla grew close to Corrin because of the concubines fighting in King Garon's harem. She never actively seduces him, she acts the same way regardless of Corrin's gender. If doting on your little sibling is seductive then a lot of people I know are trying to get into their little siblings pants ?. Hate a character all you want but don't jump on a bandwagon and become an ignorant sheep.
Edit: For some reason the reply I quoted isn't showing, whoops. Probably because of my slow computer.