That's because she's bound by rules. They're essentially chains for her. She has things that she can and cannot say. She can tell us, the dead, many more things than the living, but that's because the dead cannot effect the living world too much or too drastically.

And that's true. The story didn't even talk about the mirror having special properties, so if you're just basing it off of the story alone, then you aren't going to get anywhere. What's important is who used it and how many times can a person use it.