Hi
Is there any difference in meaning?
When she was bathing, the phone rang.
While she was bathing, the phone rang.
Thank you
There is no real difference.
Incidentally, if she were in the bath, most speakers of BrE today would say 'while/when she was in the bath/having a bath' rather than 'while/when she was bathing'.
Context is always important; labelling is rarely important.