The problem i have isn’t that when I say no, she throws a fit (ok sometimes). The problem is most often or not, when I say no, she asks “why?”
I’m not a parent yet, so I don’t have first hand knowledge, but I’d think that this is not really a bad thing, right? Kids are curious. If they question “why” instead of throwing a fit, that just mean they’re learning and they want to know the reasons behind your decision. This might allow you to keep a more open communication relationship w/ her as well. The worse you can do is say, “because I said so!”. :-), I always hated that, still do, hehe.