before receiving any dental / medical treatment or attending any lesson, get her a mask and insist her to wear that during working hours, that can prevent the whole family from inhaling 沼氣而中毒!
Perhaps got decay teeth, get her to see dentist, but pls note that the insurance will only cover emergency treatment. Better check w/ insurance company first.
Perhaps she got digestive problem, get her to see doctor
Perhaps she has not cleaned her teeth properly. Get her to attend a toothbrushing and 用牙綫 lesson (perhaps taught by you!!)