There’s a lot of set up going on on this page. First, we have the small act of Gale slicing the bread with his knife, foreshadowing his part in the love triangle to come: one of the major things keeping Katniss from allowing herself to fall completely in love with Peeta right away is the knowledge that doing so would hurt Gale. Katniss also notes at this part how much the two of them resemble one another physically - a resemblance that extends into their personalities as well. It’s interesting that it comes after Gale slices the bread, because it’s ultimately this fact that drives the two of them apart, and causes Katniss to choose Peeta over him.
Next, we have the explanation of Mrs. Everdeen’s and Primrose’s appearance, as well as the explanation as for why. Katniss’s mother left her home in a comfortable lifestyle for something she believed to be more important: love. Katniss currently only has a basic understanding of this; while she has in her a tremendous capacity to love herself, Katniss operates in survival mode. By it’s very nature, survival mode tends to be selfish. However, as we can see by how much she loves Prim and the lengths she goes to in order to protect her, this isn’t necessarily Katniss’s default nature.
Part of what causes Katniss to grow beyond this is her relationship with Peeta. The sentence, “She must have really loved him to leave her home for the Seam,” is very similar to when Peeta says he must have loved her a lot in Mockingjay. A big part of Katniss’s character arc will be learning to allow herself to love despite how scary it can potentially be. It’s ironic that she mentions not being the forgiving type here, when she more or less behaves exactly the same way her mother did first when she loses Peeta at the end of Catching Fire, and when she loses Prim at the end of Mockingjay. Forgiveness is a lesson she will have to learn in order to get beyond these things.
And finally, we have Gale spreading the bread with the cheese Prim provided. And what is Katniss’s favorite thing that comes out of the Mellark bakery? The cheese buns. :)