Usually I like brainstorming possible approaches to these problems, but this time I really come up with nothing--which to me is indicative that a professional needs to get involved, just like the others are saying. Do you clearly understand why she doesn't want to see a therapist? Maybe you'll find your way forward once you've figured out her reluctance. Is it a financial issue? Is she afraid medication will be prescribed? Does she feel there's stigma to having a therapist?
I'm sure as her partner you can help her considerably. But at the same time, and I'm not a professional, but I wouldn't be surprised if there are things that happened in the past with that ex that she doesn't necessarily want to tell you and that you maybe don't want to hear.