I was thinking of a ready cooked meal, or a ironing service, or something like that, that would help with the basics so that she can just relax. Not flowers or something to grow (though lovely, they require more time, not less in a busy schedule full of kids demands on your own).
I live too far away to just pop round with a lasagne once a week and am aware that phone calls also take her away from valuable chores and relaxing time!