What Causes Pain In Different Part Of Body When Treating Breast Cancer?

My mom is 76 years old and has been healthy as a horse. She had a brief experience with breast cancer 30 years ago, but otherwise, no aches, pains, or health problems of any kind. In the past six weeks, she is experiencing severe pain that is in different places-- hip (mostly right), lower back, neck. She also experiences tightness in her abdomen. Doctors diagnosed and started treatment of polymalgia rheumatica, but she feels that is better but these other undiagnosed problems have completely changed her life. She went out to the grocery store this week and was in much more severe pain that night. If she bends down, she has great difficulty straightening back up. Is this sounding like something specific?