Murphy shot Harry a look, as if to remind him of his own goddamn old-fashioned sense of hospitality. She still wasn't a huge fan of vampires herself, but the only thing Bill had done in this situation that she could see so far was make sure Molly got to Harry's safely. She couldn't see an angle in it for him, and she was usually pretty good at sizing up character and intentions.
Not to mention that, given the fact that Harry was living with a vampire and had willingly subjected himself to a Tunnel of Love-style mind-whammy, she didn't quite get why he was being so inhospitable to this one. Except for the fact that he wasn't a pretty (at least she assumed that Harry's vampire housemate must be pretty) female. And of course Harry's neanderthal overprotectiveness when it came to Molly.
"If it's all right with you, I think we'll leave it up to Molly whether she still needs your presence," she said to Bill in a polite tone.
And speaking of Molly, she hadn't missed the hurt expression on her face before she disappeared into Harry's room. She left the vampire and wizard alone and followed Molly.