retin-a micro is actually perscribed to some people to help oily skin.. retin-a micro is probably drying her skin out to the point where it overproduces oil.
i've always had normal to dry skin, and i've been using retin-a micro for 6 weeks- it's just beginning to work. but my skin is so oily now, it's disgusting. right after i wash (with a gentle cleanser like cetaphil) my skin is very dry- to the point where i can't put makeup on without it peeling. i don't even use a washcloth anymore because it's too rough- i just wash my face with my hands, and i let my face 'air dry'. after an hour it's oily. by washing her face a lot, using a more drying facewash, or even using a washcloth is probably going to be counterproductive.
things i've found that helped:
-using a tiny amount of retin-a micro at nights, pea-sized or smaller for my entire face. it says on the retin-a micro website that using a lot of retin-a micro will just make skin more irritated...
-this seems weird, but using a moisturizer will actually help skin return to its normal balance. after she washes the retin-a micro off her face try using a little bit of moisturizer... try one for oily skin.
-using oil blotting sheets during the day to keep from looking too shiny. you can find these at drugstores, clean and clear makes some. a tissue might have lotion on it that will clog her pores... these sheets are non-comedogenic
-using a talc & cornsilk-based powder. this helps me the most.
i hope this helped some... i definitely feel her pain, ridiculously oily skin seems to be pretty common for people using retin-a. i hope her skin adjusts to it better than mine has