Dress up party help?!

I have been invited to an Alice in Wonderland themed birthday party (we are going to have a teh party!!!)
The host has asked everybody to dress up as a particular character (as to avoid everybody dressing up as Alice) and she asked me to be the hedgehog (because I have curly hair?). I told her it was too hard and she berkata I could be the duchess.

I need to know what the hat she wears is called and how I can buy/ make one.

Any other tips on makeup/ hair/ costume would also be helpful.