I just googled the Variety review of the L.A. production of BARE, and found this quotation:
"Two performances that really steal the show are Keili Lefkovitz's sadly comical turn as Jason's slovenly, overweight sister, Nadia, and Stephanie Anderson's soul-singing, thoroughly hip nun, Sister Chantelle."
So Nadia was still portrayed as overweight. I don't think she would have worn a fatsuit -- the production was very low-budget, and it would have been easier to have found a larger actress. My guess is that she either gained weight for the role, or is already naturally voluptuous enough to take on the part. Nadia doesn't have to be really fat, just larger than the other castmates, and especially Ivy.
Variety review of BARE's L.A. run
BlueWizard's blog: The Rambling Corner
HEDWIG: "The road is my home. In reflecting upon the people whom I have come upon in my travels, I cannot help but think of the people who have come upon me."