Disclaimer: Harry Potter and The Odyssey are not mine. Nor will they ever be, unfortunately. I simply borrowed them.
She likes him because he has direction.
No- that's wrong. She loves him because he has direction.
It's a hard thing to have in times like these. After all, who do you believe? The government, the backbone of the whole world around you, or the man you've always known to be the most brilliant madman of their age? She's split on the whole thing, and thanks God all the time that there's at least one person who thinks he knows what he's talking about.
It's not that she believes what he believes to be right by any means. In fact, every day things are starting to look more and more against him. But he has resolve; he'll go down with his ship, and she admires that.
His is a strength that one wouldn't expect, because nobody expects anything from a redheaded kid with glasses, even if he isn't a kid anymore. She sees it every week when she brings burnt casserole to his drippy flat. The remains from last week are always left in the fridge, and he looks a lot thinner than he used to back when they were at Hogwarts. She always asks him why he doesn't eat, and he always replies that he'll get to it as soon as his work is done.
She doesn't like the huge menacing pile of work that he always has to carry around with him. It never seems to get any smaller, and she can see it's breaking him into pieces. She knows she can't help him, though- business is business. He slaves and he slaves, and he's almost like one of those cartoons of the men chained to their desks.
She's taken to smoking cigarettes to give her hands something to do (because he won't let her stroke his hair any more) and she's taken to drinking coffee to give her mouth something to do (because he simply can't be bothered with talking and he most definitely hasn't got time for kisses). This is causing her to lose sleep, but it isn't as though thoughts of him don't do that anyway.
She's been asked why she stays with him. After all, she's young and has a promising career ahead of her. She could have been a Quidditch star, or a singer on the Wizarding Wireless, or even an auror or schoolteacher if she really wanted to. She always replies, with fierce conviction, that she loves him, she loves him. And she says it over and over until she knows that it really is true, and she is more than happy to accept it.
When he realizes, one day, that his direction might be the wrong direction, he'll be a broken man for a while. It might be days, or weeks, or even years. He'll see his life as a shambles, because his unwavering belief is all that he thinks he has. But she has unwavering belief too, he'll find.
After all, the Penelope of legend waited twenty faithful years for her husband Odysseus to come home to her. And this Penelope would be no different in waiting for her Percy to do the same.