Hi Angi
It seems to me not a bad idea for your mother to seek help of a physio and preferably of 1 who sees neck/shoulders on a regular basis. I do get the impression your mother is not keen on seeing a physio (or are`there other reasons to fail to attend the appoinment). Maybe your mother has bad memories of hospitals, maybe she doesn't know what a physio does, name it.
I think you have told: Whiplash 1 year ago, ever since tightness and soreness of the neck, worsened since a couple of months. Poor musclemass and slight osteoporosis.
Before being able to give you any answer: How about movements of the neck/head (e.g. some painful, restricted) ? Can she get relief from or aggrevate the symptoms? Has she always pain (in the neck)or e.g. more in the morning then in the evening, how does she react in general on pain/ discomfort? What sort of pain (e.g. sharp/dull)? Has she as well pain in other areas like headaches and shoulder pains ( radiating sensations down arms, e.g. numbness/pain) How old is your mother? History of earlier problems in the area? Any examinations (e.g. x-rays) after the accident? Any treatment?