Hi and welcome to the Chiari forum.
As Dana mentioned above it could be the muscles, it could be GERD related...and some of us have thyroid issues too....has she been to her Dr for this issue?
Knowing where she is post op can help too, and if she is doing her neck exercises....as we heal we can develop stiff muscles or even scar tissue...
May we ask what was done for each surgery, and y the 2nd was needed?
I have had 2 surgeries also. I am 3 mo post op from my 2nd. I have been experiencing same issue. I just think its our muscles and nerves. They play a huge part in almost all our movements. How far post op is she?