This is a book I read in the 70s or maybe early 80s. I believe it was set in England or somewhere not in the US. It was about a young girl who had been diagnosed with diabetes. Her parents bought her a horse. She has a mean sister and I remember at Easter she got all this sugar free stuff and her sister got a big chocolate egg and she lunged for it and her sister ended up busting her head open. That’s all I remember. I hope you can help!
Could it be John Branfield: Sugar Mouse?
Oh my gosh that is it!!! Thank you so much. When I read your suggestion I was thinking it was incorrect because that title doesn’t ring a bell at all but that is most definitely it now that I found a summary on goodreads. THANK YOU!!!