Childrens'/YA historical fantasy, crows/ravens & diabetes

Fiction, probably short <200 pages paperback set in the 90s with throwback to neolithic. I read at approx. age 10 around 1994-1997. Probably from the school library in the UK, in English.

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.