Or if you dont have a sewing machine...
Black trousers, turn them up to knee. Pin a brooch to the outside of each turn up.
Baggy blouse, preferably with puffy sleeves, ruffles down the front. You could use a grown up one, if you are small ish. Tie the blouse at each wrist with some wide ribbon, you could do the same on the arm to get the puffed out look.
Wide belt, with big buckle, round the hips over the shirt, pull the shirt out a bit to puff it out.
If you have a long bit of fabric, you could make a bright sash to go over her shoulder.
Then eye patch, could use a real one, or paint one on with face paint.
Head wise, if you have a black floppy pirate hat great, other wise, a headscarf tied round her head, knotted at the back.
Legs, long white socks, pulled up, bonus points for frill around the top. And then footwear, you could either use boots, or if you have them, some nice shoes with buckles on. You could even use plain shoes and pin sparkly brooch on each.
Finally, if you can find a cheap toy parrot or monkey to perch on her shoulder, great, or just draw/print one out on cardboard.
Arrhh me hearties!!!