Oh he knew she could take care of herself, that wasn't in doubt. But he couldn't control the situations she got herself in. He couldn't know where she was or what danger she was getting herself in. So a few of his people kept an eye out. Looked out for the woman he'd fallen for, only told to intercede if she was in any real danger of being hurt. If it annoyed her it was a price he would pay to keep her alive. "I'm not going to stop them Emma, they need to be there just in case. You know how it is, I need you safe, and they'd never intervene unless you were going to get hurt. Do you know what losing you would cause? Things would...well they'd get much messier than an army of plastic people can cause."
It probably would be considered emotional blackmail what he did to her sometimes, things he said. He knew it was unfair, or at least he knew that it was perceived by people as such. People had such weird reactions to straightfoward things.
But then she told him he was all she wanted and oh did that feed the ego. He liked being the centre of attention. It was a well known fact, and coming from her. Well, Emma was one of two people he wanted to be constantly on the mind of. It meant a lot to him because he really had given himself to her, as much as he ever had done before. She wanted to be with him, she wanted to be in it together no matter what and that was all he needed from her. Oh eventually he'd have to test her. Probably by killing Jo. But she'd deal with it, she'd get past it because whatever happened, that's what she'd said.
"Don't you worry, if you're happy here then just think how much better it can get. You finding me Emma, that was fated, you do realise that don't you? And I'm a very big believer in fate and what it means. You are part of my world now, the parts you like and the parts you don't. And the parts you don't like. Well...you leave them to me. You don't have to involve yourself. You know that. I've never asked that of you, have I?"
He knew she was falling for him. He might even stretch to love, and it wasn't like the Master and that idiot woman of his. He didn't need Emma as part of his plan, he didn't use her as a distraction. God help him, he just sort of wanted her with him. It would have been so much easier for both of them without the pesky feelings stuff. And they both knew it.