Obviously she changes her clothes.
But she doesn't regenerate naked, or regenerate in her pyjamas, and she doesn't change her clothes in the Cargo Bay which again would require some nudity, even though she's fine with public nudity since she was willing to mount Harry in the Mess, and didn't give a toss when q stripped her.
We've seen her go from work to regeneration, and we've seen her go from regeneration to work. Changing her clothes for whatever reason is not contingent on her regeneration cycle.
Seriously, if circumstances come about just right and she's only going to regenerate for four hours in the middle of the day, it's not worth planning out an entire new outfit when she probably stains her clothes less while regenerating even if regenerating doesn't clean her clothes and herself... Although, if her body is just full of poisons and waste products, the act of regeneration would squeeze her like a pimple forcing all that poison and waste out... Where? What is the exit strategy of all the chemicals in her that make us feel crappy and sleepy (Not talking about poopoos and weewees for once.).
Is there a communal bathroom?
Or does she just book holodeck time for bathing?
(There's four people in my house and one bathroom. I've had to make some hard choices.)
The enlisted share quarters (Do they? I don't think they do. That was just on Enterprise.)and probably might not have sonic showers in their quarters like B'Elanna does.
Does Seven run the risk of damaging her electrical doohickies from bathing?
If the primary cleaning mechanism is the sonic shower, that completely sounds like that antiregeneration weapon I was bitching about before, that she couldn't clean herself without her personal forcefields activating because everything that had just been finely attuned with 5 hours of regeneration is just getting shook up like a snow globe.
She has to be waterproof though?
Thing is that Voyager would have a lot of Staterooms the crew wouldn't be allowed to use under normal circumstances because they're "reserved" for dignitaries and hauling regular "citizens" from one side of the Federation to the other... But such reservations would no longer be applicable since the Federation is so far away that it's bonkers to leave all that real estate untapped if they're forcing the able crewmen to use bunk beds who could be planing a revolution.