My mom has been getting body chills during the evenings for 2 consecutive days. anything to watch for? no other notable symptom. been having lower back and rib pain but that might be due to diagnosed osteoporosis?

Is she having any other symptoms of infection? If she has UTI symptoms-burning with urination, urinating more frequently, feeling like she has to urinate right away, etc., then this could be due to a bladder or even a kidney infection with the back pain. If she is having any of these symptoms, you need to at least call a doctor and if it gets worse, go go to an ER or urgent care. Good luck!