Short story regarding this situation. It's been well over two decades that I dated someone who did.I was young,and really wasn't sure what was going on. The net wasn't quite what it is today with education. Talk to her,but also highly suggest what others have with a towel,and ill tell you why. I ended up burning my mattress because she couldnt really control it like some,and I couldnt react quick enough many times. I live out in the country thankfully...So when I burnt my mattress the entire area wreaked of piss,and im talking STRONG. The person that helped me carry it out said "dude do you piss in your bed?"..it absolutely has piss in it. Noone would ever change my mind that it doesn't. If she can control it plz just ask her to let you know. If you are in a situation like I was...get a towel. Like most things,communication is key. Good luck