The least painful way to go about it, is to wean as gradually as possible. If you can't or don't want to put baby to the breast, I would suggest pumping your milk. Less often than she would eat, so that your supply goes down, and gradually decrease how often you pump. You will be in a lot of pain if you try to do it cold-turkey, no matter how much milk you produce!
And like megs said--it can take awhile for you to dry up completely. But once it's mostly gone, and you're not in any pain from not breastfeeding or pumping, it will dry up eventually without you having to do anything about it. Good luck!!
Whiskers