Hi QultingaddictUK. I know your sister will love the Bucket Hat. I volunteer in the oncology unit of my local hospital and make many hats for the patients. In the winter, I knit & crochet hats but the bucket hats are extremely popular during the hot weather. The hats are quick and easy and can be made from any washable fabric. I've added buttons, sequins, etc. to some of the hats and as they are reversible, you can go crazy with them.
My heart goes out to your sister and I hope you make her many, many hats.