Revealing mistake: When they're driving back to the Darcys' in the snow, you can see that as they pass through the village near the house, the snow on the ground is in fact a white ground sheet and has not been pulled up to the edges of the wall surrounding the green. (01:17:25)
Revealing mistake: In the first scene when Bridget makes her way up her parent's driveway, you can see her shadow against the cobbled post. However, the sun isn't out and it's cloudy, cold weather overhead. (00:01:15)
Answer: Lots of times in book-to-movie situations and even in some remakes, the producers/writers/directors change names or events. It can be because of personal issues, legal ones or it can even be spur of the moment. it can also be unintentional,when they change it without the specific INTENTION to change it. I think in this case it was more likely that the character/or their name didn't have too much of an impact on the story line, so they didn't feel a pressing need to keep it the same.