I'm not quite sure I understand what your saying here.
I don't think it's Ventress, it just seems to unusual and an extreme step from what we've seen from her before. I think it has to be someone whose known, otherwise the guards would of been extremely suspicious and wouldn't of just of been knocked out when Ahsoka first escapes.
What do you mean suspicious? Jedi weren't allowed in the facility either so a quick stealth attack would have been the only option. And if it was a Jedi who used his/her identity to gain access, there would have been record of that. But I don't really get what your saying...
It is unusual, but only because we don't have all the facts. She hates Jedi, and she hates Anakin. So at least bombing the Jedi temple is not much of a stretch, who knows what she has planned for Ashoka... but the main reason I think this is the case is because Ventress confronts Ashoka in Undercity - that seems to much of a coincidence.