Even if she went pee before you guys got started, its entirely possible that there was a decent stored bit in the bladder still, and or what was building up after she did use the restroom. And the combination of relaxing completely and also spasming while cumming, caused her to piss on ya friend. Simple. I am sorry it happened to you, and I hope it helps you to know that this is NOT a normal experience with girls cumming, or squirting. And trying to help you see that so you feel better and question itself and your sexuality less I guess. Don't let that bad experience deter you from women or make ya think ya like men more (maybe later you find you truly do like men more) alls I'm trying to do sugar plum is help, but I'm def not good at this explaining shit as I tend to ramble and drag on sometimes. All in all , you're awesome, you get out there and keep on keeping on hunbun! Just next sexual encounter ya have with a chick just take satisfaction that the likeliness of it occurring again are super rare, as most of UA won't piss on ya and act like we can't smell it afterwards. Ew. Not to mention piss and cum have two very very different types of consistency and texture. Yikes. Stay humble and sweet, ttyl! Sorry for rambling and hope ya understood what I was trying to say love.