From your description, Sarah has been diagnosed as suffering from RA, while Mary 'claims' to have it. So I'd say the former has RA, while the latter might have RA.
The symptoms of stiffness, swelling etc. can just be down to age. I don't think I have arthritis, but I feel stiff in the joints at the age of 51. Lifestyle is a factor as well.
For myself, I've been prescribed asthma medicine as I used to suffer from shrtness of breath and do suffer allergies - cats and grass, mainly. The inhalers have made a difference, but so did banning the cat from the bedroom. I don't consider myself to have asthma, just suffer from asthmatic symptoms occasionally.
People experience symptoms, but they can often be psychological. Doesn't diminish the effect, but there have been countless studies over the years where a placebo has an effect.
I can see acupuncture having an effect on the symptoms described - after all arthritis impacts the nerves to create pain, while acupuncture is also triggering nerve reactions, so there may well be some intermingling of reaction.
Chinese traditional medicine is certainly closer to the scientific method than homeopathy (let's water down medicine until it's undetectable and let the placebo effect kick in) and the doctrine of signatures (a rhino tusk looks vaguely penis-shaped, so it MUST be an aphrodisiac), so I think it's a viable route to take.
BUT, double-blind testing, etc. is a known way of assessing the efficacy of treatment. Check the studies and check the rigour of the studies...