The Courtship of Lady Macbeth

I don't really have a theory for this question, but as I listen to "Enter Three Witches" on audiobook, the idea crossed my mind.  Do you think that Lady Macbeth was, once upon a time, a nice person?  Who then turned into what we see in the play?  Or do you think that what we see is the way she's always been?

In another book I'd started and never finished, they go with the plot that she was a perfectly nice and normal woman who was forced to live at the nasty, gloomy castle Inverness by King Duncan, and this directly led to the miscarriage of her child.  In that case, the whole story plays out more like revenge against Duncan.

The same is true for Macbeth himself, I suppose, since we often speak of them as the perfect couple.  Is Macbeth just a man like any other, with his own fair share of ambition, who gets pushed over the edge by the wyrd sisters?  Or was it always eating away at him, something that would have come to pass whether the witches had anything to do with it or not?


What do you think the Macbeths' life was like 10 years before the play?