Kelly noticed that there are urinals inside the female restrooms, only that they were on the floor.
She quickly went into a stall and pulled up her dress, then pulled down her panties, noticing no difference in her anatomy- her vagina was still there, right at the same place. But what changed was that she didn't feel her bladder was full, so she decided to wish it full.
Without knowledge of how to piss as a girl, she looks at the women who are pissing at the stall, next to her. Kelly saw them just doing what she used to do to piss before the wish. Pulling down panites, pulling up skirt, then piss. She heard loud hissing sounds as the women next to her pissed.
So Kelly decided to let it loose, the pee shot out from her peehole like a laser beam straight at the urinal, the pee shot out so quickly that it pushed Kelly back, the urinal was instantly filled with 20 litres of pee in 10 seconds, Kelly screamed in awe as the piss flew. Kelly felt satisfied with the changes in her body. Looks like now women released their pee in much higher pressures with their much stronger bladders now, there wasn't shift in anatomy anyways.
After pissing, Kelly did some research on the new male and female pissing anatomy. From her research she found out that pissing contests were now undertaken by women instead of men. The pressure of piss in a girl's bladder is now 50 times stronger than men, even with their penises, men were unable to pee standing as pee drips out of their penises. The average woman can hold 20 litres of pee in their bladder comfortably and men can only hold 1. While girls don't have the penis to piss, they have sets of extremely strong muscles that compensate that. A fun fact was that a girl once pissed over 200 metres in a pissing contest setting the world record of the time
With much stronger muscles around their nether regions, woman now became the dominant sex when having sex as they can overpower men with their strong pee.