If you can get a hold of guava leaves, you can boil it and use the water for bathing or for washing the affected area. It would lessen the infection and ease the itchiness. Guava leaves are natural disinfectants.

IS IT LIKE WITCH HAZEL?

I looked up witch hazel to be sure. It acts as astringent whereas guava leaves have antimicrobial properties. I also found out that my great grandmother, bless her soul, is not just being gross when she had us drink the boiled water from the guave leaves if we have diarhea! It is scientifically proven.

You can also try this...

one part neem
two parts lavender
two parts violet
one part myrrh
one part frankinsence
mix in a carrier like jojoba or grapeseed oil.

I have found too that things like dragonsblood, patchouli, and thyme are also good for the skin.
you can give her biotin supplements (sometimes it will help with eczema and some other forms of dermatitis. make sure she is also getting enough EFA's (essential fatty acids) in her diet. Eggs(cooked untill the whites are completly done) flax seed, nuts, avacados, fish, things like that will help as well. Make sure she doesn't have any dairy allergies, or gluten allergies either, as these can be culprits as well.
Good luck dear,and let us know if any of this helped.

thank you all verry much for your help. I will try your suggestions and let you know...