If the child is only about 12-14months old I wouldn't worry about it. If the child choses to go without food and drink to hold out for mom so be it. I wouldn't get in the habit of holding the cup or spoon feeding the child but just serve the meal and clear the meal as you do with the other kids. If mom is nursing that much the child isn't starving. Since you can't make mom stop nursing there isn't much you can do. Hopefully the child isn't miserable from being hungry and thirsty for you. I would expect as the months go on the child will start eating and drinking more on their own.