She never took the catsuit off.
She regenerated instead of slept in a cargo bay that was still a common area that was used for ships necessities and functions.
She stood there awake, regenerating fully clothed, and crew walked in and out of the cargo bay because they had to.
Icheb regenerated fully clothed right next her.
The only logical nondisgusting conclusion is that the regenerating process CLEANED Seven and CLEANED the Borg children through their clothes while regeneration "fed them" and regeneration fixed all the breaking down crap in their bodies that needed constant fiddling with.
I mean despite The Voyager Conspiracy and Unimatrix Zero we do think that Seven is completely awake while regenerating and not regenerating 24 hours a day, 7 days a week?
Why didn't Harry ever invent an antiregeneration weapon? Using the same principles as how regeneration makes them fit by tightening their screws, they could have reversed the process to loosen everything to make them unfit.