Probably because she didn't know how to go back in time and save Danny- she needed the Doctor to take her back in the TARDIS. Also, even if she could control the TARDIS, the Doctor would know what she was doing and stop her.
I think because she was in dream state herself and very emotional at the time. The doctor actually just wanted to see what she would do and how desperate she was, how fast she would go.
Clara did this because even though it opens with the snap of a finger I would think that あなた still need the key to be a key and the keys to the tardis are o powerful that I would think that the tardis some how would know that the keys were destroyed and would think t was for a reason cause who whould destroy all of the keys and without the keys the tardis would most likely just shut itself down.
