I've been going thru the same problem! Gracie was so traumatized by water (didn't even like the water dish - she would go up and over that area of the cage to avoid it).
After I messed up with upsetting her badly by just holding a water bottle I switched tactics and let her watch me from the shower curtain (I was careful at first to not splash any water) and made a really fun, happy noises & clucking type of sounds - she was very interested in my performance lol.
I did try using a pesticide type container (brand new) that had a fine mister setting thinking if she didn't hear much & feel a strong squirt - this didn't work for me but others have had success. So I had to beg forgiveness & pay her off with a treat.. again.
We have made quite a bit of progress lately tho, when I noticed she was looking way more relaxed on the curtain rod I reached up and tried a step up .. once she choose to step up I placed her at the dry end of the shower away from the water stream. I then pretended she wasn't there and resumed my "fun" within a few minutes she ran up to my feet and started trying to catch the water with her beak. She eventually starting playing under the water. I don't push her & I end it when she shows signs of "enough" and retreats without returning to play. Lots of talking & praise and excited "fun" noises and upbeat tone of voice really gets her attention. Of course a lot of "good girl" etc. when it's all over.
The next day she played in her water dish for awhile (feet dipping and beak dipping) was a huge step for her!
It's a learn as ya go process & I've "angered" and upset Gracie a few times I just change my tone of voice to a commiserating, apologetic one, put her in her favorite spot and bribe her with a treat & await the princesses forgiveness
Good luck! sure do have to think outside of the box with these diva's
