Hi Thanks for your querry. The cause for swelling of the enlarged lymph nodes in the groin may be due to a drug reaction, allergic reaction, benign cyst, cancer (lymphoma, testicular), hernia, infections in the legs, feet, or pelvic area, and STDs (sexually transmitted diseases). The swelling in most cases goes away without any treatment, though if the conditions turn serious, it is important to seek medical aid. I think she should visit a doctor, because the lymph nodes are not returning to normal size since long. To relieve the pain you can try warm compresses, draining, surgery, or take over the counter pain relievers, prescription anti-inflammatory medicines and massage therapy.