I know of several BCs that have developed this issue. The answer, I think, all depends on what you want to do. If she seems healthy enough and is not getting unduly stressed by the hustle and bustle of a town then some positive persuasion may work. Be firm in your encouragement for her to follow. If she follows the lines of others that I have seen once she has "won" this hurdle she will go for the next and the tail will be wagging the dog! Try and entice her with her favourite treat to break the pattern and then reduce rewards apart from words of praise and encouragement (but don't overdo it). If she is still behaving in this way then a vet check up would do no harm.