Azula smiled at Yang, but saw she didn't know if she could trust her. She pulled back her hand and asked "So Doctor...have you figured this out?" 
"Almost. My TARDIS 50% power. Once she has 100% percent we can move."
She?" Azula asked
"Oh yea the TARDIS is alive. She has a soul." The Doctor said
Azula rose a eyebrow in disbelief.

Doom knew this to be true. He heard the voice. Doom had to get the Doctor out of her.