In the case of Johanna, they each hated each other because that was what the Capitol had taught them to do. They were from competing Districts, and the idea of the Games was to keep the lesser citizens of Panem distrustful of one another and unwilling to form alliances (or raise arms in war).
Katniss's next most significant relationship at the start of the series is her friendship with Gale Hawthorne. Gale is her best friend, and he loves Katniss very much. He wants her to run away with him but Katniss is too loyal to her mother and sister to ever leave.
Up until almost the end of the book, Katniss is mad that Johanna betrayed her and tried to kill her in the arena. She sees it like this: Johanna knocked her out, cut her up, and left her for dead. It's not until the very end that Katniss finds out that Johanna was working to save her life.
Devastated and left mentally and emotionally stranded , Johanna spent the next few years in isolation, wallowing in her sorrow and trauma. During this period of time, she served as a mentor for the tributes reaped in her district.
The Life of Johanna Mason (Hunger Games Explained)
Why does Johanna hit Katniss over the head?
Katniss Everdeen
Even though the two were now allies, they still didn't trust each other. During the escape from the arena at the end of these Hunger Games, Johanna 'attacked' Katniss for the purpose of removing a tracking device from her arm, then lead Brutus and Enobaria, the District 2 tributes, away from Katniss.
Peeta later explained to Katniss that Johanna did this to get a reaction, since she and the other tributes obviously saw Katniss as being the most "pure" of the Victors.
She is angry she wasn't informed of the plan and lashes out at him. Despite the fact that Haymitch has been working since the very beginning to save her, she cannot forgive him for letting the Capitol take Peeta alive.
During the supposed execution of Snow, she instead shoots Coin, due to her being responsible for Prim's death. She then attempts to kill herself with the suicide pill attached to her uniform, but Peeta stops her.
Unable to find Peeta and hearing a cannon, Katniss nearly attacks Finnick, suspecting his betrayal, but he reminds her to "remember who the real enemy is." Katniss attaches the wire to an arrow, firing it into the arena's roof just as lightning strikes.
Katniss made the choice to build her future with Peeta. If she didn't love him, she wouldn't have made that choice. Katniss made her whole world about getting the people she cared about to the next day, her choice to survive with Peeta proves her love for him.
When Katniss comes home to District 12, Gale immediately confesses his love for Katniss, and she realizes she might have feelings for him, too — but she can't explore them, because she has to continue her fake relationship with Peeta or else her entire family, including “cousin Gale,” will be killed.
Johanna Mason developed an addiction to morphling while hospitalized in District 13 for the torture she endured in the Capitol. When she was weaned off, she instead dipped into Katniss's supply.
Ever since their first meeting in the elevator, Johanna Mason has had her eye on Peeta. Even though she came off as cold and distant, she was never afraid to show her admiration for Peeta. In that same scene in The Hunger Games: Catching Fire, Johanna asked Peeta how he felt now that everyone wanted to sleep with him.
Johanna and Katniss take the first watch that night. Johanna tells her that Mags was Finnick's mentor and half of his family. She also tells her that she was with Wiress and Beetee because of Katniss. According to Johanna, Haymitch said if she wanted to ally with Katniss, she'd have to have Wiress and Beetee with her.
Snow laughs after Katniss killed Coin because he enjoys the irony of the situation. He avoided the official execution ceremony, even though Panem's citizens still take their revenge on him, while Katniss ends up snatching away the victory and power that Coin thinks she has successfully secured.
Prim tried to stop Katniss since she knew she would most likely not survive the horror of the Games; but Gale Hawthorne held her back. Katniss' bravery was strong in this part. Gale taking Prim away at the reaping.
Katniss feels betrayed, most of all by Haymitch, who used her and Peeta. Eventually she wakes to find Gale there. He's badly injured and tells her the Capitol bombed District 12 after the Games. He got Prim and Katniss's mother out in time, but the District 12 is gone.
Although she will never know for sure, Katniss does recognize that she cannot be with Gale. She will never be able to forgive him for his idea — the parachute bombs — that killed Prim.
Later, the two learn President Snow considered their actions to be an act of rebellion against the Capitol. After their last interview, in which the two continue to affect their romantic feelings for one another, Peeta comes to the realization Katniss has staged her love for him all along.
Chaff, of course, comes right out and kisses Katniss, though his reason is more to have fun with Katniss's image than to turn it to his advantage. Finnick's and Johanna's tactics, however, are clearly deliberate attempts to manipulate Katniss, and Katniss immediately distrusts both as a result.
While the Hunger Games film never talked about it, the Catching Fire novel explained why she could only communicate through hand gestures. Katniss briefly mentioned that a previous stroke could have caused Mags' garbled speech. However, post-traumatic stress disorder could have also caused her speech incapacity.
Johanna pretended to kill Katniss and dug out her tracker. She then led Brutus and Enobaria away from Katniss and they followed Johanna. Johanna was captured by the Capitol but was rescued by District 13.
