I don't think any of us realise how our relationships and feelings can change about parents. When we're young, they're a fount of wisdom and support and know it all. Then as we grow up and accumulate experiences of our own, it becomes easier to judge by a different set of criteria. Also, we tend to see our mother and father as our parents and are never really able to judge them dispationately as individuals in their own right, as perhaps, we would judge a neighbour from across the road or a work colleague. If your mother simply won't discuss the trigger points for your blow out, there's not much you can do. Perhaps she felt your husband "let you down" when your business hit a rough period, but the important thing is that you and he have pulled through together, and perhaps she's a little envious of your strong reltionship together.
Are you sure that it's not your being overweight that is really the issue that is bugging you and making you feel unkind about yourself. Try and be honest with yourself about this, and if it is damaging your self-esteem, make some determined efforts to try and deal with it. Perhaps your mother is also going through the Change, which is making her ratty, and also making her feel that some of the best parts of her life and now behind her. Knowing that you're growing older and less attractive isn't much fun, so perhaps it's better if you just focus on the good points of your relationship with your husband and daughter, and leave her to work her own way out of her miseries.