Teenage girl. never had oily skin, now whole face is oily. will this ever get better/get back to normal skin? would birth control pills reduce oil

Yes, this may: change to become less oily, once you are through puberty, although there is never a guarantee. Birth control pills regulate hormone levels and are used for some girls to treat acne, especially if other treatments are not helping. Please discuss this with your doctor if you're considering that treatment.

Host likely hormonal: Depending upon the age, teenager skin start to get more oily in these turbulent years mainly due to changing hormonal profile. It happens in both sexes, more severe in some. Pimples often exacerbate the situation and should be treated diligently and consistently to avoid scarring later. In most cases, it is a temporary period, so relax but get your daughter checked regularly by their doctor.

Possibly: It will reduce the oiliness indirectly by reducing the amount of sebum produced by the skin. As we go through our teens the amount of sebum produced increases. Only 3 brands of birth control have been approved by the FDA to treat acne however, so this does not apply to all BCPs, and if you don't have an acne issue and are not seeking birth control there are better ways to control oily skin.