While comparing the characters of Jemima and her Broadway counter-part 
Sillabub, I noticed these things:

1: Costume
   Jemima wears a mainly black and white costume with a brown, red 
and white wig, while Sillabub's is more of a fawny colour, like 
Jellylorum's.  Jemima wears two leg warmers but no arm warmers, 
however, Sillabub does.  Jemima's wig is slightly twisted at the end, 
but Sillabub's fluffs out more, like Bombalurina's.

2: Character
   Jemima is almost certainly older than Sillabub, however, they are 
both the youngest in the tribe. Sillabub has a cuter 'feel' but 
Jemima has a more haunting presence. Jemima's voice is a strong 
soprano while Sillabub has a slightly smoother, melodic soprano. 

3: Makeup
   Not many observations, but Sillabub has painted eyelashes while 
Jemima has more makeup under her eyes. Jemima's got sort of a 
purplish shade of lipstick, while Sillabub's is pinkier.

4: Names
   Jemima means, as I said in my earlier description, "peace". 
Sillabub derives from the name of a pudding which is made from fruits, 
cream and alcohol and is very sweet but a bit naughty (the whiskey or 
brandy)!

by Luna