I got a similar text message from my girlfriend several weeks ago, minus the crazy talk about drowning kids and never waking up again.
We're back together now, but I don't want to give you false hope. We've been together since 2003, and this last year of our relationship has been so good that I finally proposed to her. She felt really guilty that our big plans will be delayed by four years, until she finishes getting her undergrad degree and then law school. So she wanted me to find somebody else that would make me happy. Since then, I've helped her to understand that I am happy, but also nearly as busy as she is, and patient enough to wait for summer break. We're happy together, so there's no sense in ending a good relationship.
Your situation is different, because your lady needs help and knows it, but refuses to get that help. You aren't happy together anymore, and she knows that it's her fault. But she isn't willing to change, for you or herself or anybody. So there isn't a healthy future together in the cards for you two. She is trying to do the right thing, as she sees it, by setting you free. I think that you should get in touch with her, and go through with the breakup. You will both get a sense of closure, and then you can move on and find somebody who really wants to be with you.
Good decisions come from experience. Experience comes from bad decisions.