Likely answer

Morvern Callar: The Novel About a Woman and Her Dead Boyfriend

The book is Morvern Callar by Alan Warner. In this 1995 Scottish novel, the titular character wakes up on Christmas to find her boyfriend has died by suicide. Rather than reporting it, she leaves his body on the kitchen floor (and eventually disposes of it), steals his unpublished manuscript to publish under her own name, and uses his money to travel to the Mediterranean.

Confirmed match: Morvern Callar by Alan Warner