Hi, you should always check the original movie credits (where she is credited as "based on the book by"). IMDb is a good secondary source, but the data is user sourced and errors do happen. In this case, however, the error is most likely related to IMDb getting their writing data from WGA and not from the actual credits. I submitted a correction to IMDb, but it's clear they prefer the union credits over the actual movie credits in these cases. Thanks.

One more note: Whenever you see a locked credit on TMDb, it usually means that the credit has been verified against the actual movie credits.