SOLVED. Believe the title was Buried secrets. Description contains spoilers [s[

[Cheyanne]

In the story, the main female character is married to an emotionally abusive husband, but stays with him since they had been friends since they were children and he had helped get her through the disappearance of her brother when they were kids. In the end you actually find out that the brother died because the three of them had been messing around and he got locked in a car in the garage with it running and died of carbon monoxide poisoning. They panic and hid the brother's body, and she somehow managed to block it all out until things start getting bad with her husband and he reminds her of it. Could swear I have the title right but every book brought up with that title doesn't fit the description. Read the book between 1993 and 1998.

[Cheyanne]

Never mind, I found it. It was Buried Lives, happened to find it in some old pictures that had my bookshelf in the background. Yay!!

[Kate]

Buried Lives