It’s not a happy ending, but neither is individually in a bad place nor sick or dead or with anybody else, Izzy just…can’t really be tied down in one place and even though they seemed like they were doing well, she left. Really, she left them all, the rest of her team, the other protagonists too, so…she’s just like that.
I don’t know if the show’s renewed and if it is, I don’t know if Stella will be back, it seems like it’d be too repetitive a story, Izzy would need to beg Stella’s forgiveness again after leaving abruptly, but if she comes back within a short enough time, or actually deals with her shit, I could see them having a future.