This Question is over the to and rude... sorry
Ok CR is said to have bought those panties herself.
I assume she had on a second pair of panties under the white panty to keep them clean... I'm not sure how long a film day is... but is she was just in one layer I can see that being a problem because people wear them for a reason.
My guess is that she bought a bunch and kept the wash and on the set.
I'm sure she she felt a bit exposed...