How do you cancel a business partnership?

We haven't actually open shop yet, or even gone into paperwork to make it official. I told my good friend that I planned to open a store within the next six months and said friend asked if I would like a partner. I said yes, because we seemed like minded at the time. It has only been about a month, but I can now see that my friend cannot keep her sights on the business goals and is an impulse buyer (willing to spend a lot of money on very little). I am not like that and cannot run a business someone of that nature.
My question is, how do I politely say that I no longer wish to have friend as a partner?
(as a side note, friend has not done any work on the business plan or with the wholesalers (as I had already completed these things before friend offered), has not contributed financially, and the business plan has not been altered to include a partnership, and has not yet contributed finacially)

Simply tell her that you've decided to go it alone. Tell her NOW and save yourself a whole bunch of grief...