When I ordered this it had been listed as "California Costumes Women's The Mad Hatter Costume,Multi,7-9" and I did buy it direct from Amazon, not a 3rd party.  I got it and the packaging says "Teen." They've amended the listing to say "Teen" now.  Do keep that in mind for sizing.  And why don't I just list the sizing off the package while I'm at it?  That would help, right?

Junior (3-5) Fits up to 34" Chest, 27" Waist, 34" Hip, 65" Height, Weight up to 110 lbs
Junior (7-9) Fits up to 36" Chest, 27.5" Waist, 36" Hip, 67" Height, Weight up to 120 lbs
Junior (11-13) Fits up to 38" Chest, 28" Waist, 38" Hip, 68" Height, Weight up to 135 lbs

So there's actually not a massive difference between a 3-5 and a 11-13, I guess.  1" bigger waist?  lol

I squeezed into my 7-9 but if I were a half inch bigger in any dimension it wouldn't have happened.

Teen sizes.  Just remember that these are teen sizes.