How do I go about spreading the word properly about a terrible wedding vendor?

uming your lawyer thinks it's a good idea for you to be putting your story out there before you file any formal complaints, try Angie's List. They're considered a reliable source for weeding out good vendors from bad ones, and they've got a whole section for weddings. You could also post to complaint sections on wedding forums, or write to any wedding publications that carry ads for her, or try and get your local paper interested in an expose. It depends how much effort you're willing to put into it.