I agree with the previous poster that it sounds like submissive urination. Definitely visit your vet to rule out any urinary tract infection or urinary crystals/stones though. Your vet can also give you some advice on dealing with submissive urination. Some dogs grow out of it, others don't. If you have the time to get her involved in something like agility it may help build her confidence. That can sometimes help submissive urination and also its a great outlet for a high energy breed like a border collie.