Have her take it off IMO- either the buckle or studs will rust, the stitching will rot, or it'll go mouldy from not being able to dry properly. So will her neck!
More importantly a sub should always be clean & fresh
A good point from Oz about reading through the posts & info on the forum- don't just rely on this thread. Try the search button.
(Oz often says wise things & is usually worth listening to)