Always address this issue with the person first before going above their head. They may not even be aware they are doing it and a whole host of issues can come from bypassing them, when it might simply be taking care of with them and there are better relations in the company when doing so as well. If not resolved with them, then it is time to go to the person above them.

Having been in a similar position before, I asked if I could to talk to them about what happen the other day (or rather previous days as it was a common occurence) as something has been concerning me. I pointed out that I was concerned about her reaction the other day when I asked about (whatever it was) because from my perspective I ask questions in an effort to learn more and to better my understanding of the organization, the roles, and to help support her and the company, I was not questioning your judgement and apologize if it came off that way. I hope I can come to you when I do have questions. Are you open to this and is there something I can do to help meanwhile?

This will give you a better idea of her position as a manager. It could open up a great dialog for better communication and less snapping. Perhaps something along those lines might be a way to approach her for better relations so you are not having to walk on eggshells around her and can approach her easier in the future.