Hi, welcome to Health care magic forum.
As you correctly think, it must be there even before starting the exercises, as these have started after starting the exercises, it must be due to the myalgia, or may be due to the defeciency of the calcium or other electrolytes.
Any how you are consulting your doctor tomorrow, ask him to not talk of the
fibromyalgia, with her to prevent psychological factor.
Avoid giving her potato, other tubers, tomato, egg, chicken,
and sea foods till the pains are cured.
Wishing for a quick and complete recovery.