It's boring. She's so... ordinary. Yet at the same time, he doesn't mind. She's not boring. For now. He can use her while she lasts. Yes, that's all. A temporary toy. When Sherlock dies, he'll make sure she's gone as well. He tells himself that he'll get rid of that thorn in his side that is Molly Hooper. Molly Hooper who makes his chest feel warm and his skin tingle. Molly Hooper who likes cats and watches Glee. Molly Hooper the morgue attendant who giggles during autopsies. Molly Hooper who was completely in love with Sherlock Holmes and not him. He told himself he'd get rid of her.
Then again, Jim Moriarty was never known to be a very honest man.