Why does Katniss give her mother an intense lecture? What is Katniss worried about?

Katniss's mother and sister are allowed to see her, and she quickly lectures them on all the responsibilities they must remember to fulfill so that they can not only survive but also prevent Prim from taking tessarae. She is particularly stern with her mother, demanding that the latter not fall back into the self-pity that had paralyzed her after her husband's death. Though she promises Prim she will win, Katniss is certain it's impossible, considering the bigger, well-nourished and better-trained kids from wealthier districts.