This is an interesting assignment, as it really stretches the rules of the Hunger Games themselves. The tributes weren't allowed to take anything into the games, so it's hard to imagine how they would create a post on social media. Additionally, you have to navigate the fact that they wouldn't want to give away any information about their current situations, as that would be detrimental to game strategy. Therefore, I would recommend allowing for a setting (you may want to note at the top of your assignment) that these posts are within a private and hidden group.
The chapters cover everything from Katniss's reaction to Peeta's profession of love for her to the moment when Rue points out the tracker jacker nest over Katniss's head. It is written in first person point of view from Katniss's perspective, so finding information for your "posts" for her would be easiest. That would be my recommendation.
Here are some highlights from each chapter that may help with ideas for your posts:
- Katniss reacts to Peeta's professions of love.
- Katniss makes final preparations to enter the arena.
- Cinna encourages Katniss just before she enters the arena.
- Katniss enters the arena and the games get underway.
- There are immediate deaths.
- Katniss ends up with a pack and a knife as she heads for the woods.
- Eleven tributes die the first day.
- Katniss believes Peeta has joined with the Careers.
- Katniss learns that the Careers are using Peeta to try to find her.
- Katniss begins to suffer from dehydration and hopes a sponsor will save her. (This doesn't happen.)
- Katniss finds water and a "wall of fire" descends on her.
- Katniss receives some bad burns from the fire.
- The Careers find Katniss, who makes it twenty feet up a tree to save herself.
- The Careers resolve to deal with Katniss the following morning, and she spots Rue in a different tree near her. Rue points to a tracker jacker nest above her head (although we don't learn what this object is until the beginning of chapter 14).
Haymitch shouldn't comment. One of the primary concerns Katniss has during these chapters is trying to figure out what Haymitch is thinking. For example, when she needs water, she doesn't know why Haymitch won't help her. Some good options for people who could comment are Katniss's mother, Prim, Gale, Peeta's parents, or basically anyone in District 12. Although there are some Capitol members who like Katniss (Effie and Cinna), I don't think they'd risk a comment, considering the power of the Capitol. I think the comments would be overall encouraging, telling her to hang on or to continue fighting. And Peeta's parents might be able to convince her to not judge their son harshly and to believe in his character.
I hope this helps as you organize your thoughts. It is tricky because of the nature of the Games and the fact that Katniss couldn't have really had access to the outside world; that was part of her struggle all along. However, your teacher is likely looking to see that you can recognize and summarize important plot developments well.