This treatment is being suggested on bases of the information provided. However I would like to examine & investigate your mother  in detail. Control  Hypertension, Diabetes or any other metabolic disorder, if there is  any. Any way it may be tried, --. Dolokind Plus (Mankind) [Aceclofenac100 mg +Paracetamol 350 mg] 1 tab. OD & SOS. X 5 days. --. Caldikind plus  (Mankind) 1 tab OD x 10 days. (You may need help of your local doctor to get these medicines.) --. Fomentation with warm water. Let the part not be exposed to cold. --. Sleep on a hard bed with soft bedding. --. Use no pillow under the head. --. Avoid painful acts & activities. -- .Do mild exercises for  neck and shoulders. --.(Take help of a  physiotherapist). --Do not ignore, let it not become beginning of a major problem. --Do ask for a detailed treatment plan. Kindly make sure, there is no allergy to any of these medicines. --For emergency treatment visit nearest hospital. --Wish your mother a quick recovery & good health. --I hope, I have solved your problem to your satisfaction.  Dr N C Gupta MS (ortho)

Is your mother 50 yes old? However normally after certain age both shoulder and neck are involved with some wear and tear within the joints of neck and shoulder joints as well .both of them make a vicious cycle and anyhow it takes atoll on the patients pain levels. Try painkillers followed by physiotherapy and this should help. If not better  after a trial of 2 to 3 weeks meet a orthopaedician and he will guide you.

Try physiotherapy

There are two possibilities one is could be a muscle pain due to neck muscle strain, second could be due to shoulder strain causing pain to radiate from neck. Need to be examined and treated accordingly

What you have described looks like a muscle spasm, Physiotherapy would help.