That does sound familiar to me somehow. Maybe because I ought to be doing better than I am too. And I'm struggling to figure out why. I do have low self-esteem, and that could be related but the only way to find out whether or not it is for her is to hear what she has to say about it. I think that lack of self-efficacy makes more sense. I can't speak for her, but for me I think that I feel things will never be "good enough" no matter what I do, so why bother?

She could also have unmet caretaking needs that stem from childhood. Maybe she learned that people will abandon her or reject her if she does things for herself.

You're asking interesting questions. Why do you think that you have been unresponsible and lazy in the past? Have you tried talking to her about what is going on? Would she be willing to go to counseling and work on it?