I would mention it, albeit casually, along the lines of 'I don't remember breaking a mug, do you? the hotel have charged me for it, how odd'. If she denies all knowledge, at least you have brought it into the open, and someone else may well be responsible. I do remember someone, many years ago, stealing a towel but making sure they took it from another room, not theirs. Otherwise it is going to fester, and you are going to find yourself examining the contents of her china cupboard on your next visit.
I have noticed on recent hotel visits polite notices advising that attractive items such as decorated water bottles, mugs etc can be purchased from Reception, and- not-so polite notices warning that missing items (towels, bathrobes, cushions, lamps (!) will be charged for. Apparently people do not regard it as theft.