Looking Glass Girl by Cathy Cassidy.
Hardback first edition, with dust-jacket. Published by Puffin (2 April 2015). Also available in paperback and on Kindle.
272 pages: aimed at 9-13 year olds.
Cathy Cassidy (born 13 June 1962) is a British author of young adult fiction and has written over 20 books.
From the publisher:
Get ready to fall down the rabbit hole all over again with Looking-Glass Girl.
Alice is thrilled when Savannah invites her to a Wonderland-themed sleepover; she’s wanted to join this circle of friends for so long. Finally, she’s fitting in. But an accident suddenly changes everything and Alice is rushed to hospital.As her friends and family rally round, a mystery begins to unravel. Was Alice pushed, and why? Who would want to hurt her? Can her loved ones – and the gorgeous boy who doesn’t want to leave her side – help Alice survive?
Looking Glass Girl is the stunning new book from Cathy Cassidy, an unforgettable tale of friendship and love from one of the UK’s best-loved authors.
On Amazon for around £12.
Alice in the Internet 
I have, and have read this book. And although I’m not 9 to 13 years old (!), I thought it was quite fascinating.
Ha ha! Recommended ages are not necessarily right: just look at Harry Potter!
Or “Alice in Wonderland” for that matter…
Age range for the unabrigded book is 9 to 11 years according to Amazon…
But :
“Some day you will be old enough to start reading fairy tales again.” according to C.S. Lewis…