You can use a flat iron on the lowest possible setting to make her hair smoother. Wet her hair, put in a lot of conditioner, divide her hair into sections, and quickly run each section through the flat iron. It does make a bit of a mess, but her hair will definitely look smoother afterward, although it may not make her perfect, depending on how bad the frizz is. Just be careful not to over-iron, because it'll make her hair frizz up again, and it won't get any better. Oh, and make sure you're super careful doing this, because, obviously, plastic melts.