Barring any physical/medical condition, I'd hazard to guess that this is a an example of your dog assuming the alpha role and that the solution to your problem is to teach the dog that
you are the alpha dude in the pack (your dog sees you and your family as
her "pack" and
she's the boss).
Dogs aren't that complicated (unlike humans
) and I'll bet that needing to understand that she's not the leader of the pack is all she needs to be shown.
Sounds corney, but check out that Cesar Milan guy, "the dog whisperer". He's dealt with the situation you describe on a number of his TV shows.
It would be a shame for you and your family, and the dog, to turn her out if this is the problem.
Good luck.