I believe the book you are looking for is called "This Body: A Novel
of Reincarnation" by Laurel Doud.
From Publishers Weekly:
"On midsummer night, June 21,3 9-year-old Katharine Ashley dies of a
heart attack in Northern California. The mother of two, whose
worldliness consists of having seen the film Woodstock five times in
1970, wakes up a year after her death on a squalid bathroom floor in
L.A. She finds herself trapped in the drug- and alcohol-dependent
body, and in the unhappy family of 22-year-old photographer and
all-around gilded youth Thisby Bennett. Without any of the
discomfiture one might expect in such sitcom circumstances, Katharine
navigates Thisby's world, which includes a harelipped sister named
Quince and an all-too-attractive brother called Puck. Determined to
save everyone (Quince, Puck, her own children and Thisby herself),
Katharine discovers much about the temptations and risks of mothering
and second chances..."
Paperback: 304 pages
Publisher: Back Bay Books; 1st Back Bay Pbk. Ed edition (February 8, 2000)
This book is avalable for purchase from Amazon:
site:.amazon.com woman died "wakes up" body girl drugs
I hope this is helpful. If you have any questions regarding my answer,
or believe this is not the book you remember, please don?t hesitate to
ask for further assistance before rating.