What's the Name of That Book??? discussion

So I recently reread Gone Girl and while I was reading it I kept getting the plots mixed up with another book that I had previously read, this is basically what i remember from it....
Wife goes missing and during the investigation a diary is discovered (similar to gone girl) but the diary is typed so there is arguments about whether or not it is really her diary.
I remember that the couple has a daughter, the mother didn't really like being a mom and she had to pretend that she cared...I also think she may have munchausen??
Don't know how it ends but I basically just remember that both the husband and the wife ended up being pretty psycho.
Sorry if this isn't enough or seems all over the place but if you have any insight please help!!
Thanks so much!

Do you remember when you read the book? What about any memories of the cover? I'm assuming adult, yes?

i read it about 2 years ago, can't remember the cover. but yes definitely adult fiction

A guess - The Wrong Mother (also: The Point of Rescue) by Sophie Hannah?

Haley, what can you remember about the family's background or occupations?
How about the location?

Oh yeah, it does sound like The Wrong Mother. I've forgotten some (many) of the details but there is definitely a diary supposedly written by the mother but the reader is not sure if it really is written by the mother.

yes!! it is The Wrong Mother! Thanks you so much!

Great! Glad we could help. :)