She used to think he was just quirky. Different. That it was all just a side effect of his genius. But lately she's been seeing the compulsive tidying, doing things by threes, the dissecting and categorizing of his life, as something pathologically painful. She used to open the door before he was finished triple-knocking, or parrot his crazy back at him. Now she waits, impatient, but knowing that it pains him when she interrupts. Like nails on a chalkboard or the squeal of styrofoam, the twisting, gnawing wrongness only assuaged by the completion of his routines. Maybe it's not healthy, but she finds it helps to think of him like a robot, or a computer; you can't interrupt him halfway through a process without deleting all his progress, or crashing his operating system, or whatever.
She used to think maybe he could be fixed if he was interrupted in a way he couldn't get past. Like maybe he could be forced into normalcy, into ordinary function, if there simply was no way for him to resume or restart his usual routine. She used to try. Just in little ways, because she's not a monster, couldn't bear to be the one who broke him for good, no matter how much he frustrated her. She knew it wasn't fair, though, to take out her frustrations on him, when the problem was so much her own. He lived his crazy, supernaturally ordered life, and it worked for him. It was on her that sometimes when he was lecturing her about some dumb thing she'd said, she couldn't tear her eyes away from his lips. Or that her body hummed with awareness of him sitting beside her on the couch, eloquent hands illustrating the crazy-brilliant-genius that pours from his mouth in a vaguely twangy monologue.
It's her problem that she wants things from him that he will never be capable of giving. Maybe in order to be that damn smart you can't have any brain left over for living; it's all taken up with quarks and monopoles and string-thingies.
So she keeps doing her thing with Leonard, and watches the crazy roommate slowly unfold into something almost like a person. If his moments of empathy are learned behaviours instead of actual human connection, she tries not to let it bother her. Tries not to read anything into the small moments that feel like they're real (large, warm hands splayed across her back, arms circling, awkward, but so sweet her eyes almost sting)(take it, I'm not using it, take it)(soft kitty, warm kitty, little ball of fur)- it would just hurt more the next time he callously disregarded her in favour of his own well-being.
Her heart grows cold to him over time. They interact less and less. She tries so hard not to let her disappointment turn into resentment at the arrival of Amy. Tries not to think about how if only she was smarter maybe she could have been the one to turn him into a real boy. But then she watches them, sees the way he pulls away from Amy with every breath, retreating twice as fast as she can advance unless she catches him unawares. And thanks her lucky stars she never really fell in love with him. That hurt belongs to Amy now, that always-reaching, never touching, emptiness.