Because the Teller was tired. Note that her next action was to take it back into its hibernation pod.

The Doctor : (Reading her perfectly) You're scared.

MS DELPHOX : I’m terrified. I have the disadvantage of knowing Karabraxos personally.

THE DOCTOR : If you don't like your boss, why stay?

MS DELPHOX : (A cynical smile) My face fits . Now, if you’ll excuse me, I must take the Teller to its hibernation. (to Guards) You two, dispose of our guests.

And she leaves with the TELLER in tow.

Because the Teller was tired. Note that MS Delphox's next action was to take it back into its hibernation pod.

The Doctor : (Reading her perfectly) You're scared.

MS DELPHOX : I’m terrified. I have the disadvantage of knowing Karabraxos personally.

THE DOCTOR : If you don't like your boss, why stay?

MS DELPHOX : (A cynical smile) My face fits . Now, if you’ll excuse me, I must take the Teller to its hibernation. (to Guards) You two, dispose of our guests.

And she leaves with the TELLER in tow.