As soon as I saw her played by Helena Bonham Carter in the fifth Harry Potter movie, I had to sim her.
Meshes:
Dress by rose: http://www.rosesims.org/clothes/roseclothes_5.htm (the middle one)
Hair by Sussi: http://sapphiresims2.com/showthread.php?t=22581&highlight=sussi (it is the only place I can find the mesh, which is included)
Nails by shadylady482: http://modthesims2.com/showthread.php?t=190393
Jewelry by Lianasims: http://lianasims2.com/ (go to accessories page, then download Mesh 03 adult at top of the page. Also, go back a few jewelry pages until you see a link for mesh 02, download that as well)
Other:
Eyebrows/makeup helaene: http://www.helaene.com/
Skin is a partless recolour of Louis'
Mesh recolours by me
Enjoy!