Not Quite Dead Yet by Holly Jackson

In seven days Jet Mason will be dead.
Twenty-seven years old, she’s back living with her parents, waiting for her life to begin. She’ll do it later, she always says. Her parents have their doubts. Until, on the night of Halloween, Jet is violently attacked by an unseen intruder. She suffers a catastrophic brain injury. The doctor is certain that within a week, she’ll suffer a deadly aneurysm.

Jet never thought of herself as having enemies. But now she looks at everyone in a new light: her family, her ex-best friend turned sister-in-law, her former boyfriend. She may only have seven days – if she even makes it that long – but Jet is absolutely determined to finally prove her doubters wrong.
Jet is going to solve her own murder.