CPAP machine as hand luggage

After flying for more than 5 years with a CPAP machine (in its own bag and marked). I was loadly harrased by a safair air hostess (Confidence Mababa) this morning at ORTambo domestic departures about having an extra hand luggage piece.. I explained that the bag contains a cpap machine and that its a medical device and should not count as hand luggage. Mme Mabasa insisted it counts as hand luggage and threatened that if I cannot put the cpap bag in my handbag, I would have to go back and pay for an additional bag. Which would most likely result in me missing my flight. Either Mme Mabata is wrong or Safair should inform business travellers that have a cpap with them that (different fom other national and international airlines).they see medical devices as part of your hand luggage allowance so we can choose another airline