The reason she gets 'upset' if you don't let her out when she wants is because she can't hold the wee in!!! Cats do not enjoy peeing in the wrong place, especially when they've been doing it in the right place all their lives. She needs to go when she needs to go, and if you don't let her out right away, of course she will have to do it elsewhere!!!
Oh, and cats don't spray out of 'spite' either - unneutered toms spray because the owner forgot to neuter them...