Would you still feel the woman was still in the right if her parking had caused an accident? Would you excuse her from using common sense and still blame the sign maker?
Why wouldn't I? I don't know enough about campers to know whether or not a non-"motor vehicle camper" is a real thing. Apparently it's not. I didn't know. She might not have known either.
This is why signs need to be clear. There are instances where common sense can trump a sign. For example, a Yield sign on an on ramp that gets hit by a car so that it is now facing highway traffic instead of the ramp is very obviously meant for the ramp. You see enough of those that you can make an informed decision that you still should yield to highway traffic.
I don't know what that monstrosity is. In fact, looking at it, I have to wonder why they didn't just make it "No parking for more than 24 hours." What is allowed to be there? Perhaps they should have said X parking only instead of this weird list of exceptions.