Ok...this poor little girl...what she must have endured 
You defininately did a good thing by rescuing her from that. Now its time to be very patient with her. First thing you need to do is have a vet run a complete exam...if you have not already done so.
If this is not a medical problem and is more of a mental condition there are options for you. You could discuss the use of prozac with your vet for your girl. This will help with her separation anxiety as well as taking the edge off.
Dogs that piddle and roll over are showing you submission...not necessarily out of fear...its showing the utmost respect. (although we don't really seem to think so)
If she does this when you call her, call her more often...ignore the problem..do not scold her for doing so...as frustrating as it is, ignoring it will solve this so much faster...just simply clean it up. Call her to you many times throughout the day and give her a great treat for coming to you. I am going to post a site for you regarding "submissive urination". This will give you a start on how to work with her. She may or may not ever get over this habit. Another option to help is a doggie diaper, but really try to work with her first.
http://www.dogdaysusa.com/behaviorcenter_urination.asp
I wish you all the luck and keeping working with your little girl...she loves you for it :) Let me know if I can further assist you :)
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