I used the Bloomer Buddies "Oh Sew Kat!" pattern which is available from Pixie Faire to make the dress, though I wish I had added more fullness to the dress below the yoke, as it falls too straight for my liking . . . which of course means I will probably make her another dress to wear before too long.
The beret, scarf, fingerless gloves and leg warmers were adaptions I made from a Kiltie Combo Accessories knitting pattern to fit 18 inch American Girl Dolls by Jacqueline Gibb on Ravelry.
As Merida is a 16 inch doll, I simply used size 2.75mm needles instead of the 3.25mm and knitted it in one colour throughout. The scarf was knitted horizontally in garter stitch, rather than vertically like the pattern suggested.
The brooch on the side of the hat I made myself and the Joyce Nicholson boots she is wearing I had in my stash. These soft real leather boots were originally purchased at a bargain price from a doll fair long ago . . . always knew they would come in handy some day. :)