There is no gravity aboard Elite: Dangerous ships. Not even when docked. As you might notice, when you dock in the zero-g environment. Not even there you could bathe.
The only place you can bathe would be in the luxury apartment towers sticking out of the station where there is the most gravity. And your ships stays near the centre of the station, so even when you elevator down there would be no gravity to speak of. That is in fact why that big Imperial ship has this rotating ring, to create gravity for the hot-shot passengers. The rest of that ship will see no gravity at all.
But by all means, let your personal sense of immersion collide with the facts of the game. Just ignore the lore and have yourself a merry little bath.