Read your contract if you have one.
Also the Email, Carefully.
If there is no mention of repossession then she would have to get a court order allowing her to repo the vehicle.
If there is, She would have to allow for the specified time to elaps.
If she has written you an Email stating that there is to be a late fee assessed after a certain time, Then that would be the same as allowing a grace period and she could not repo untill it is obvious that there is no other solution.


