She tightens her hands on his, lowering her head and letting out a shuddering sigh as she considers that. "I don't want to be away from you," she says, and looks back up at him, her expression pained. "But it might be for the best."

She can't guarantee his safety, as much as she wants to. But this might protect him for a little while, while she and Sherlock run down their leads and figure out what exactly is going on.