Crazy doctor who theory

One of the weeping angels survived from angels take manhattan 

It slowly travels accrossed country to the West over a century

In the 22 century after the Doctor left her there, Susan and David travel to America to help rebuild after the dalek attack and end up in the west. 

Susan gets touched by the angel and she gets sent back a hundred years

She attempts to make a crude vortex manipulator, but our technology is to primitive and instead of going forward a hundred years, she goes back another hundred, now in the open plains of western America 

A few Native American tribes men find her, mistake her for a settler, and become enraged.

They attack her because she's alone, but she manages to escape but she's mortally wounded

She wanders a little while longer and finally collapsed in a field and regenerated, the only other creature in the field being a wild mustang 

Including another theory of mine that unless exceptionally talented, a time lord/lady's regeneration is random or based on their thoughts at the time/what's around them, Susan ends up regenerating into a stallion not unlike the one that was in the field with her.

She wanders a bit longer, gets caught by wranglers who "tame" her, and she ends up being sold to a minister who names her Joshua and moves to a town by the name of Mercy.

....my mind is a very strange place where things like this happen....

Anyways I hope you like this theory. Please tell me your thoughts!