[quote=Schradinger]
Should there be a shield from behind which the master has to watch?
[/quote]

Yes. It is the command room she's stuck in, after all, so it has a very powerful shield. The separatist leader must so be scared, trapped in the same room, just the two of them, with a jedi master. She could capture him but is trapped in the room so has nowhere to take him. They are both captured until the other battle is concluded and the winner lets them out.