giant platelets are abnormal platelets which are not able to do their function of blood clotting as normal sized platelets would do. this abnormaility arises from the source of origin of platelets in the bones. considering the blood clots
under the skin it is clear that your mother has a platelet disorder.
her bodyache , myalgia which has been diagnosed as fibromyalgia
then also comes under question.
would suggest to see a hematologist
and get a bone marrow examination
done. there seems to be an undiagnosed problem.
feel free to discuss more.