Greasy Sae is a "bony" old woman who sells bowls of hot soup from a large kettle at the Hob in District 12. Katniss Everdeen and Gale Hawthorne traded with her often, and made a conscious effort to keep on good terms with her as she could consistently be counted on to buy wild dog as most of their other customers could afford to be more picky. Greasy Sae seems to make just about anything edible. Katniss mentions a winter specialty of Greasy Sae's that includes mice meat, pig entrails, and tree bark. She also mentions in passing a wild dog and rhubarb stew. She calls any meat beef when it's in her soup. She also has a granddaughter that Katniss describes as "not quite right" who wanders the Hob, and is generally treated as sort of a pet by people in the Hob, who give her scraps of food from their stands. Greasy Sae is not directly mentioned in the The Hunger Games film, but a character who is presumably her is seen dealing with Katniss. She gives the mockingjay pin to Katniss, although in the book, it was given to her by Madge Undersee. Greasy Sae appears in the Catching Fire film, where she is pushed onto the ground by a Peacekeeper. Before he can beat her, Gale jumps on the peacekeeper, saving her.
Katniss reveals that Gale told her that it was Greasy Sae who started up a collection in the Hob to help sponsor Katniss and Peeta during the 74th Hunger Games. Katniss helps repay that kindness by continuing to shop in the Hob and making it a point to visit as many vendors as possible. Greasy Sae also reminds Katniss that during her participation in the 74th Hunger Games, Gale was considered her "cousin."
Greasy Sae is among the 800 survivors evacuated by Gale after District 12 is bombed by the Capitol following the end of the Quarter Quell. In District 13, Greasy Sae works in the kitchen, which she likes well enough, but notes that the cooks are lacking in imagination. She is happy to receive real beef from District 10, noting that it's not the wild dog that Gale and Katniss used to provide her with. When Haymitch calls people to tell stories of things Katniss did that inspired them, Greasy Sae is among them. While she is not specifically noted as talking, its mentioned that many people brought up what Katniss did that was so inspiring so she may have been one of the others. This leads to the decision to have Katniss not do scripted lines as the Mockingjay. During Finnick Odair and Annie Cresta's wedding, she got up and started dancing with Gale. At the end of the book, Greasy Sae is one of the few hundred people to return to District 12 following the war. When Katniss returns to District 12 after the war, Greasy Sae comes over in the morning and evening to cook and do light housekeeping, with her granddaughter, who Katniss says "lives in her own world." Whether this was because she was being neighborly or because she's been paid to do it, Katniss is not sure. It is not known how long she keeps up this arrangement once Peeta returns to District 12.