It's a waste of time mate, she'll be the one to decide what tidy is when she gets here. However it is when she arrives, she'll just see it as a blank canvas anyway. The best thing you can do is just find an out of the way cupboard somewhere and move all of things that you like to have lying about and handy (but which are never in their right place) into it. Then when she arrives, just tell her that she can re-arrange the house in anyway she wants, but YOUR cupboard and everything in it must stay as it is.
Iain.