It sounds like she has difficulty managing her time and her responsibilities. While reading your initial post, your description of her behavior made me think of how ADD manifests itself in women (quite different from how ADHD is for men). Has she ever looked into that possibility? Women aren't usually diagnosed until they are adults (and they are usually in the “predominantly inattentive” subtype, rather than hyperactive).
ADD, or ADD tendencies, makes it hard to prioritize and handle multiple tasks. One is often trying to catch up with promises made and live up to responsibilities, because there is usually some disorganized thinking and forgetfulness, as well as the frequent need to be hyper-focused on something or someone, and it's hard to meet day-to-day adult expectations. Women with ADD tend to be disorganized, forgetful, stressed out, and extremely sensitive to criticism. There are websites where a person can fill in questionnaires to see if they lean toward ADD. I don't think it would hurt to look into it.