Make her a mountain man shirt, leggins and a breech cloth from scratch.
The shirt can be made from muslin about $2.00 a yard and the leggings from canvas. I would use wool for the breech cloth.
You can make the patterns easily by using old paper bags or freezer paper. Cut the paper into the general shape and tape it all together with duct tape or some other suitable substituion like box tape. Once you have the outfit the way you like it, cut it off with scissors. Be carefull of course. Lay the pattern on pre-washed cloth and start cutting. Be sure to add in seam alowance and your there. The whole making a costume with paper is a very interesting endevor and quite a teaching aide. The pattern of course is re-usable and exactly the right size, no messing around with the wrong size pattern. Don't forget to add a gusset under each arm for easy movement of one's arms. A gusset is a square shaped piece of cloth that adds extra room under arms an in the crotch of a pair of mans pants. Not needed on a breech cloth and leggins of course.
You can do this with any clothing including mocs and a hat. Just make the pattern with paper and tape, cut it apart and transfer back to cloth, leather or whatever.
Regards
Loyd Shindelbower