Other mistake: The last name in the credits from the cast is called Melinda, when in actual fact, the character in the film is called Melanie.
Other mistake: When the two gents are fighting in the restaurant Hugh Grant tackles the guy through the plate glass window and they land on the street. Two points: 1) How do they not receive any cuts from landing on shattered plate glass. 2) Check out the glass laying on the street. It is cloudy, a main characteristic of breakaway stunt glass.
Other mistake: When Bridget's friends come over to her home they always need to call up first. She then can buzz them in by pressing a button that unlocks the building's main door. Yet when Bridget first runs from her flat after Mark with just her bare feet you can hear her feet crunching on snow. She then runs back inside to put on her shoes and a sweater. If she really needed to buzz her friends in then there should have been a hallway where she ran first and not the outside directly. [As an addition: when Mark comes to Bridget's door to show her the newspaper article, as he says ...'I may have come at a bad time...' you can see a hallway behind him. When she runs outside at the end of the movie there is, for some reason, a different set outside her doorway. For example, when Bridget opens the door to run after Mark, it looks like she is running into bright sunlight - lighting way too bright for hallway illumination and especially out of sync with the evening sky.]
Other mistake: When Bridget and Mark kiss at the end, he puts his coat round her. The coat is huge! It's obviously specially made because before it wasn't as big as that.
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.