i made a dress.
1. get some knit fabric
(i got the end of a bolt of some random $3.49/yard knit)
i think it was a little over 2 yards, which was PLENTY!
2. make up a pattern copying what your sister did
3. make a tube of fabric for the top
4. fold that tube in half
this will be the bodice
sew that to itself (just make a hem at the bottom of the tube that you folded.
5. make another long (or short if you so choose) tube of fabric
this will be the skirt.
6. sew these 2 pieces together.
knit doesnt have to be hemmed b/c it does fray and just rolls up
so it's perfect.
so you can wear the item as a skirt (see figure 1)
or a dress (see figure 2)