Hi Luckee! I'm sure that Susan and Jacob would know each other a fair bit, and get to know each other more since he's also Molly's Watcher now. I know she'd get a kick out of running into most of your other characters as well, as she's a lover of knowledge and all.
Susan doesn't have much witchy tendencies specifically, but she does have a fair amount of knowledge that she picked up from the Watcher's Academy, so they can share a bit!