River just kind of gave a look that said 'well you can hardly blame me for trying' and then shrugged her shoulders. "You know what I mean. You have enough people in this ship for a lynch mob. I wouldn't put it past most of them." She'd seen some of them. Of course the Doctor would try to keep everything under control, but she didn't know how good of a job he was doing at that.
It was true that she couldn't be trusted. The only thing that you could trust was that you couldn't trust her. How likely was it that she was going to try something on the ship though? Probably very low, but still she understood his precaution.
She gave a snort of amusement. "He's not my master anymore. Haven't you heard? I've been let off the leash. I'm looking for something, and it has nothing to do with you. This is just a means to an end." Clearly Mr. Slayer was something of a sore topic with her, but she would try not to get too angry about it.