I was unfortunate enough to go thru the summer in South Georgia with a wig. I chose a lightweight wig from www.beautytrends.com. My son plays baseball all summer long so I bought a couple of hats and wore them with a wide headband at times. Unfortunately, it's going to be hot no matter which way you go. Just tell her to experiment with different things until she finds what suits her best.
Jeremiah 29:11 - "For I know the plans I have for you," declares the Lord, "plans to prosper you and not to harm you, plans to give you hope and a future."
Hi! I'm sorry that you sil is having to go thru this. I had several different wigs that I would wear only when I would go somewhere that I felt it was necessary to look "normal". Heck, not only didn't I wear my wig much I also didn't wear my prothesis. Hated both of them.
The hats and scarves that have the hair attached at the bottom are great. You might want to suggest that she go to her beautician before she loses her hair and see what she/he suggests. There are wigs that are very lightweight. Tell her to make sure that she does have something on her head in the sun as the scalp can burn very quickly. Also, her insurance will probably pay for the wig if she uses the phrase "hair prothesis".