Great. Thanks for the additional information. I really appreciate it.
I actually suspect this is submissive behavior, rather than marking behavior, since she's "afraid" of everything.
Submissive urination occurs when a dog feels threatened. It may occur when she's being punished or verbally scolded, or when she's approached by someone she perceives to be threatening to her. It's important to remember that this response is based on the dog's perception of a threat, not the person's actual intention.
In your dog's case, she submissively urinates as a way to tell other dogs that she will defer to them and that they're in charge.
Submissive urination may resolve as your dog gains confidence. You can help to build her confidence by teaching her commands and rewarding her for obeying.
Getting her involved in an obedience class (where you'll strengthen your bond with her as well as help her develop self confidence) You should also gradually expose her to new people and new situations and try to make sure all of her new experiences with other dogs are positive and happy.
With a lot of patience and some really yummy treats as rewards, most dogs can be trained out of this behavior.
As an additional training aid, if you believe this behavior is fear based, you might want to consider using a product that is geared specifically towards anxious dogs.
A couple things you could try would be:
Melantonin is an over-the-counter drug that can be used to treat some anxiety issues in dogs. The dose you would give would be up to 3 mg given orally whenever necessary up to every 8 hours. More information can be found here: http://www.petplace.com/drug-library/melatonin-melatonex/page1.aspx , which includes risks, warning signs to watch out for and other bits of useful information.
Try a DAP collar. These are collars that are impregnated with a man-made version of the dog appeasing pheromone, which is a pheromone that nursing bitches give off to their pups to help them feel calm and secure. It's something that humans can't smell, but it has an amazing effect on dogs with anxiety and other issues. Although you can find them at your vet's office..you can also find them online at places like Amazon.com and Ebay for much cheaper. Just make sure they're DAP brand, as they seem to work better than some other versions
I hope this helps!!!