The cut-throat world of craft stores and ethics; what would you do?

A group of three of us will be opening a new gallery just meters from a shop we all belonged to. We left the shop because it was being taken over by someone we felt was unethical, dishonest and constantly talked out of a hole in her head. There were 9 of us working together in the original store, and because of this woman coming and taking over things, all but three left.
While making plans a few weeks ago at a cafe near the shop, us three were spotted by her husband. Word must have gotten back to her and she phoned the proprietor of the cafe at home that night and asked her what we were doing and talking about in the cafe. The poor cafe owner didn’t know what to say and sent us a message saying how awkward it all was for her. Initially we all felt horrible about putting the cafe owner in the spot, but then quickly realised, it wasn’t us, it was the woman from the old shop who was responsible. Now, what would you do? Would you go talk to the woman from the other shop and tell her what you think of her? Would you write an email to that woman and her partners to let them ALL know what she did? Would you leave it alone?