Ditto everyone. She now has your number, where originally it might not have been about getting out of a bath
I use an adjustable shower nozzle to bath my horses.
I have two with serious back issues. During bath season, I know when their backs need a visit from the chiro because they will move away from the water hose as soon as the cold spray hits the area that needs worked on
Once the chiro works on them, they're back to enjoying a bath on a hot humid night, to get the yukkies off them.
Your horse has now picked up an obnoxious and unacceptable bad habit that needs fixed.
I would not tie the horse to bath her (yes she needs to learn to stand tied, just not during bath time) but I would beg someone experienced to hold her and give you some guidance on getting her bathed before she lets loose with a back leg and sends you to the ER