Yooo someone else with a penchant for Lolita style! Fun, fun. I'm currently working on a gory Alice in Wonderland costume.
Anyhow, I already saw someone mentioned Mey-Rin from Back Butler, but Lizzy is great too! She's kinda annoying, but super cute, and secretly a badass with swords. Additional bonus: adorable blonde ringlets and lots and lots of petticoats. Like at least forty.
If you decide to go as Lizzy, find someone willing to roll their eyes a lot to go with you as Ciel. Good times, cosplay is the absolute BEST. I wish you luck!