For her boots, I would probably try to find some basic brown boots and add the "turn over" out of a bought fabric - attach it inside and then turn over just like a real cuff. I looked in the Hyrule Historia just to be sure and turned cuffs are definitely right.
I had to find some brown boots for Link and I searched on eBay "knee high brown boots [my size]" and found some pretty decent things. The ones I ended up with were $35 after shipping and although they are not the highest quality they look okay - but it depends on your budget. You might even be able to find something locally like at an "end of winter" sale or in a thrift store.
For the leggings, I'd look for either dancewear - thick tights or those "winter" leggings that are of a thicker fabric. If you don't mind a more "tights" feel, welovecolors.com has great tights - I have a pair in orange and they're really opaque.
Not sure about contacts, I've never used them, I'm scared of putting things in my eyes. >.< I've seen great recommendations in the makeup forum, though, and I'd tune the specifics depending on if I wanted to look more cartoonish or more realistic. Depending on if you normally wear contacts or not, it might be a good idea to practice wearing them before the convention - and make sure they are fit correctly. If you want to go realistic you might even be able to get a free sample or something from your eye doctor !
Disclaimer : This post written by a Grumpy Old Man
Actually in the pipes:
- Remaking Ser Loras doublet.
- Luke Skywalker, A New Hope
- Wind Waker starter costume in swim material
Eventually: Paul from Dune, Faramir, Harry Sullivan