Any chance of Bedbugs? Apparently they are making a comeback:

http://savannahnow.com/accent/2010-06-08/bed-bugs-making-comeback

Have you ruled out hives - see urticaria information. There is no bite mark on the bumps and the hives usually disappear within hours.

Does she have cats - if so look for the bite mark where the flea or other insect bit her. I have used both pennyroyal and diatomaceous earth to kill fleas. Fleas are the intermediate host of cat Tapeworms and the Tapeworm ova may have infected her. There are both medical and herbal remedies and supplements for tapeworms. See the 'cayenne challange' in messages by Loricalady at the Curezone parasite Support Forum.

She could have skin infections with bacteria or yeasts. The simple zappers I've used do not cure these. Most of my skin irritations were due to gluten sensitivity (Celiac Disease) which is often undiagnosed.