Oh I am sorry to hear that. Hopefully some more experienced folk will respond to your thread in the emergency forum.
I have only done it once - the idea is to get their undercarriage in the warm water - so that sort of depth. Everyone says, and my experience too is that they rather like it and relax.
Good luck and I hope it works - the idea is to help her relax so do it somewhere familiar if you can. Also, give her some calcium - again most people on here say calcium citrate is absorbed faster than calcium carbonate, but either will do. I just use human pills from the pharmacy.