just give her a bath every night and don't use soap at all
all what u can use is johnson's shampo for sensitive skin
let her wear cotton
make sure she doesn't sweat a lot ,
just use water and avoid soap or even shampo if u want
also change her shampo or soap that u use,make sure u wash her cloths with good washing powder or liquid and ,rinse in water twice

and don't worry alot of babies get these things
but u better see a doctor if it last more than a week