Cadi's in the northeastern part of the Bannorn (up near that river whose name starts with an "H" and is otherwise obscured by the blue line), so the party will be running into her fairly soon. Honestly, the easiest way to recruit her is to offer to pay her, but if the party runs into her when she's dealing with bandits/wolves/insert mook of choice and helps, she'll stick with them for a little while out of gratitude and then make up excuses to stay around because dorfs are awesome. Or she could bump into along the road, stick with them because it's safer than traveling alone, and then make up some excuse to not leave when they reach the West Road because fighting a broodmother sounds like an awesome fight.
Apologies if that's too vague to be helpful. I don't really have my heart set on any one recruitment scenario and want to be as flexible as possible.