This could be done in part, because the equipment was very inexpensive. Not much money was involved in tooling so that basic changes of that type could be accomplished.
No matter what the character is, I just say to myself 'If I, Melissa George, was in that situation, how would I react?' and once you do that you can just go for it, and hopefully the performance comes through.
If something anticipated arrives too late it finds us numb, wrung out from waiting, and we feel - nothing at all. The best things arrive on time.