Furuncle on Left Cheek. The right way?

She is having a furuncle on her Lt.Cheek since 3 weeks. Using Antibiotics: Augmentin Duo & now Zo Cef CV. Sonography done. In that report it is written: "A tiny 1.3x1.0x0.3 cm sized irregular collection with dense internal echoes is noted limited to the subcutaneous tissues of Lt.Cheek-likely to represent a chronic furuncle". Then doctor made a small cut on that furuncle & drained it completely & had put a single stitch & removed after 2 days. Its been 4 days & again puss is forming inside it (came to know by pressing). Doctor is now telling to get reports of blood & urine for sugar & to drain it again.(Yet to get reports & yet to drain it). But, I can confirm that there is no sugar because the cut made by doctor healed very quickly. Please confirm what needs to be done to cure it permanently? Is the doctor investigating it in the right way? Help with this as being her friend I can't see her in this position for so long. U'r help will be appreciated greatly. Regards, Nikhil.