When my LO had it I used camelina and lavender body oil from this company:
it worked like a charm
No not baby oil!! Mineral oil is so bad for the skin. During her next bath get her little head nice and wet and then pour a bit of apple cider vinegar on a soft wet wash cloth and very gently rubbing in circles. Not too much V and make sure the cloth is nice and warm and wet.
Cradle cap is caused by bacteria and the V helps kill them, as well as remove the flaking skin.