Robert Picardo mentioned in an interview that Jeri Ryan was sometimes late to the set due to her wardrobe (not late to work). I'm new here and I have seen a lot of people try to justify Kate Mulgrew's behavior for one reason or another but from what I've read (especially the recent release The 50 year mission vol 2--Robert Beltran doesn't hold back!) and watched conventions on Youtube, including one where Kate Mulgrew admits to being embarrassed about being unkind to Jeri Ryan, it seems like it was mostly one-sided, uncalled for and over the line.
I'm sure things were tense and there was a lot of pressure but being mean/unkind or wanting to forbid your coworker from any bathroom break (The 50 year mission is a very interesting read) is pretty wrong.
That being said, it is impressive to own up to it, especially in a public manner the way that she has.