Usually this mean a muscle problem. I got the best result using ice. Or, if someone is available to do this: cream the area, then apply wet heat, followed by massage and a linament.
If it looks swollen to the eye, I'd see a doctor. This could indicate an underlying problem that needs to be attended to, unlike your ordinary chronic stiff neck which doesn't look swollen. Why not find out?
I have read about your wife's symptoms. I agree with Paxiled. I would take your wife to see a doctor, your family doctor if you have one is preferable.
Your doctor may be able to give you a referral to a chiropracter.
In the meantime, my suggestion would be to put an ice pack on the back
of her neck. Ice may bring down the swelling. Cold is better than heat.
I myself go to a chiropracter and I have neck issues so I know what I'm
talking about. Definitely she needs to be seen by your family doctor
with a possible referral to a chiropracter and the sooner the better.
Goldenrod is a herb that is used to reduce swelling and stiffness