It is common to FEEL the need to pee when your G spot is being stimulated and sometimes when the clitoris is stimulated as well. I used to feel this way when I was close to an orgasm and had to learn to relax and let it go and I NEVER actually peed! If it helps her, just tell her she can pee right before any sexual activity so she KNOWS she won't have to go.
Squirting is something some women do and some don't. There isn't any way to do it. It happens or it doesn't. Most women I know do NOT squirt and still have incredible orgasms. From what I hear, some of the women that do squirt say sometimes it isn't even an intense orgasm when it happens. So don't worry if this doesn't happen with you two. No big deal! And less of a clean up afterwards