They'd been entwined so closely for so long, him having no one but her to lean on. He'd had no one else to talk to and now he did, and Hermione wasn't the only thing in his universe anymore – so she had to learn to share him. She didn't particularly like it all the time, but she recognised that it was natural and that how things had been, had been unhealthy for them. She couldn't be the entirety of his world.