If you look at the chairs it's the same chair. What if Jenny crash landed on the Dalek asylum and the fall caused her to regenerate? Also, since she is a Time Lord, what if she somehow figured out how to time travel?
This episode kind of irritated me. I mean, so much for him loving Rose! He just kinda left her to be cut up by creepy clock men. I guess he liked being doted on by a rich, beautiful woman. Who wasn't Rose.