What's the reason for soaking? Is she in distress, not eating/drinking or was the soaking to give her bottom a clean up?
If she's getting a poopy bottom, then you can just rinse her bottom well, then use a hair dryer to dry her before putting her back with her flock.
A bulge under the vent...
Please post photos of your hen and her poop.
What do you feed, including treats?
How old is she and how long have you had her?
I would still give her extra Calcium for a few days. You can find Calcium Citrate with D3 at stores like Walmart, CVS, etc. Give her 1 tablet daily. Just pull down...