hello H.,
poison oak responds poorly (spreads and itches more) to heat which is created by acidic foods (sugars, very sweet fruit and anything that breaks down fast to sugars like breads, cereals). excema also is better with ph balanced diet.
best to alkalinize her body to cool it down with anything in the vegetable category or lemon juice in water or foods (i know it seems like it would be acidic but it isn't). or you can put just several granules of baking soda in water which will alkalinize it.
also, light cotton gloves (acrylic will be too hot) while she sleeps will help her not spread it and there are alkaline poison oak soaps. also you can keep her cool physically with cold wash cloth compresses behind her neck and/or under her arms.
good luck!
A. m