My sister is ecperiencing a dull nagging pain in her right gtoin area for three eerks now. In this period of time shs bern helping my mother move.?

? Muscle strain. Your sister may have "pulled" a muscle. It should get better if the symptom has started to improve. Otherwise she might have developed a hernia or something similar, in which case she should see a doctor.
Get checked. She could have strained a muscle, or she could have a hernia. She should have it evaluated to find out what it is.