This isn't my usual style, but I wanted to have a go and I'm past worrying about whether or not it'll be any good, I'm just gonna go for it. Enjoy.
Sometimes she hates him. Really and truly detests him more than she can give words to.
In the same way that anyone hates anyone they love, she supposes. The way she hated her mum when she was younger, slamming her bedroom door and screaming into a pillow until her voice gave out. The way she hated Mickey for being human, for not paying her attention or frustrating her or bring happy with his life when she was not. The way she hated her dad for being stupid enough to walk out in front of a car when it had been drilled into her since the day she could walk that you should always always look when crossing the road.
And it passed. She's never been any good at holding a grudge. She still isn't. It's like trying to hold water in cupped hands – no matter how hard she tries, it drains away until she's forgotten why she was so angry in the first place. She just never thought it would happen like that with the Doctor.
She hates him when they argue for the first time and he storms out of the flat. She hates that she worries and cries and waits for him to get back, because she misses him even when she cannot stand him. She hates him when he refuses to talk about why he can't bring himself to grin at her across the room, and she assumes it's because of something she's done. How is she supposed to know if he won't talk to her about it?
She cannot stand him when he forgets about going to see her mum and dad for the fourth time, claiming that his work at the university had kept him too busy and that he's lost track of time. She loathes the way he still cannot quite bear that she works for Torchwood, seeing his eyes stray to her standard issue gun – stubbornly set to "stun" – in its holster hanging on the peg by the front door, each wince when she mentions her job lodging a little shard of anger into her heart.
She hates him when they fight, she loves him when they make up. She loves the make up sex too, and yet it's still there, love and arousal mingling together with tiny sparks of hate that leap from her body to his as they remove each other's clothes with frantic motions, whispers of "sorry" and "my fault" and "never again" released into the darkness as they move together. Afterwards the hate is always gone, not allowed to linger once they've each accepted the other's apologies.
She hates that he is so naturally charming and effortlessly flirty without even realising, hates herself for being jealous when he talks to anyone. She travelled farther than any of these other people could imagine to find him, and a tiny little part of her mostly rational brain just wants to lock him up in their bedroom and keep him to herself for as long as they have together.
She hates herself for it, because she knows that he loves her – knows it deep down inside her with every beat of her heart – so why should she feel jealous or threatened by anyone else. Doesn't she trust him?
She hates him for France. Still now, after all this time and everything they've been through, she cannot quite forgive him. They thrash it out one night after one too many glasses of wine, sharp, cruel words hurtling back and forth across the living room like knives. He tries to tell her he's already apologised, that nothing happened, that he understands that he was wrong, and she hates his big pleading brown eyes and the way he stretches his hands out as if he wants to hold her. She snarls and curls in on herself like a wounded animal, old scars ripped open and bleeding as she realises how much it hurt her at the time, how much she had pushed it down inside her and pretended it didn't matter to protect them both.
She hates the empty space in the bed next to her when she slams into the bedroom and he doesn't follow. He stays on the sofa, and for the first night in a long time she falls asleep without the feel of his body next to hers, radiating warmth and comfort and home, even in the rare moments that they aren't cuddled up together.
She hates how much she misses him when he's not around. The fact that she has lost the independence she had whilst hopping universes has not escaped her, and she detests the fact that she has become someone who cannot live without another person. Despite this, and despite the fact that they do have other interests, and they don't spend all their time together, and they do have a reasonably healthy relationship, she still craves his company.
She hates the fact that he cannot seem to grasp the concept of turning things off. The TARDIS took care of a lot of those kinds of things for him, she knows, and there are only so many times a person can have to get out of bed to turn off the TV, all the lights and the oven before they snap.
She hates the way he sometimes still dismisses things she says, the old Time Lord arrogance surfacing and reminding her of his old self, all sharp blue eyes and brooding silence and that leather jacket that she still connects with him, even after he's completely changed both his appearance and his species, sort of. He talks down to her and she pulls a certain face that lets him know he's gone too far, her eyes widening in mutinous anger. Mostly he backs down, but occasionally he carries on regardless, seemingly thinking that proving his point is worth the argument it will inevitably cause.
She hates that he is aging. She absolutely adores the fact that he is aging at the same time as she is, and thanks any amount of nameless deities and entities such as luck and fate for this second chance. What she hates is the signs that they are both growing older: the first grey hair that appears on his head, the lines growing slightly deeper around her eyes, the first time they realise they can't run as fast as they used to. They are getting older, and that means that her time with the Doctor is growing shorter every second. Such a human response to the inevitability to death, she thinks.
When she asks the Doctor, he admits that he thinks about this a lot – half-human, he reminds her, I have that miserable, melancholy part of being human that makes you think about these things. The only way they can get through it, he tells her, is by reminding each other every day that they are living their lives together, just as they wanted. And he does remind her. Scrawled on post-it notes that he sticks to the cooker, written in her lipstick on the bathroom mirror, whispered against lips and traced on bare skin with fingertips. Reminders to enjoy the present, not worry about the future. She loves him for that.
She has to come to the conclusion that she hates him because she loves him. It might be confusing and backwards, but it makes sense to her. Why would you hate someone that much if what they did didn't matter to you? If they didn't matter to you, more than anything?
She finally tells him about these tiny moments, the times where she cannot truthfully say that she loves him with every fibre of her being. He raises an eyebrow before he reveals that he feels the same way. He hates her so much because he loves her so much, he tells her. And it's logical, and she's logical and so is he, so she finally accepts it. She's always going to have moments when she hates him, and he will hate her right back. It's part of who they are and what they've become together – there's no changing it now.
Sometimes she hates him. But only sometimes.