I am a girl and every time I talk about sex or read about erections I need to pee is that normal?

Yeah, that's kinda normal. :) You may be getting a little bit sexually aroused/excited - not enough to make you wet or get your clitoris stiff or anything, but enough to make it tingle down there. You feel that slight tingling feeling as the urge to pee.

Many girls (and boys) also feel the need to pee after masturbating or having sex, partly because of the leftover tingling feeling like the tingly urge to pee, and partly because pee (especially in boys, but somewhat in girls) helps wash away fluids and clean the reproductive tract.