YA crows/ravens & diabetes

I read this book in the late 90s in the UK and parts of it have stuck with me. I would love to find it again and re-read it. What I remember:

Female main character. Her father has died/been killed in a hit and run. She sees a flock of corvids - I want to say crows but might have been rooks or ravens and they recur through the book. She has a brother who is diabetic. She somehow ends up going back in time to a primitive possibly stone age society. The tribe leader in that time has two sons who end up finding a beehive and eating loads of honey. One of them gets very ill and she realises he is diabetic and saves him with her brother's insulin. I can't remember how it ends.