Found: Children's/YA novel; fairies and fantasy; coming of age?

Hello! I remember reading this book about 10 years ago, and it was already well-loved so I think it may have been published in the 80s or 90s. It was a slim novel with one of those classic covers of an illustration of a garden, I think.

The most plot I can remember is a father dropping his two daughters off at their grandmother's house for the summer. (I believe their mother died.) Some key moments I remember:
-He takes their photograph in front of the house and tells them to get some sun because they look "wan."
-Their grandmother has a garden that she tends to very lovingly, and every time she finds a slug she flings it over the hedge with uncharacteristic fury.
-The younger sister gets sick (maybe?) and has a huge collection of stuffed animals.
-They find fairies in the garden, which are illustrated in the book.

I loved this book as a child, and I would love to find it again! I've been trying to remember it nonstop for the past week... please help!

bump

Oh, this is triggering a vague memory. I will try to think about this. It is such an ethereal memory that I can't grasp anything but what you described

I spent a long time looking for this book a few months ago. I also only remembered those same details. I came to this website to look for a different book and found this post. I'm glad I'm not the only one who remembers it. I loved it too!

>4 rarm: That's absolutely it!!! Thank you so much!