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).
Johanna attacked Katniss to take the tracker out of her arm, so that once Katniss was in a District Thirteen plane, the Capitol could not track her. Johanna had to attack her because it also had to be seen that Johanna was breaking the alliance between the tributes.
Johanna remains in the Capitol for quite a while, and she and Peeta are tortured for information concerning District 13 and the mockingjay rebellion. While in the Capitol, Johanna's entire head is shaved, making her bald. Johanna after she is rescued from the Capitol.
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.
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.
The Life of Johanna Mason (Hunger Games Explained)
Does Johanna actually hate Katniss?
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).
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.
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.
The female Morphling, however, appears almost coincidentally, and Peeta even mentions that they don't know her real name. Given that she is willing to make the ultimate sacrifice to protect Peeta, it's safe to assume that the Morphling was committed to the rebel cause.
This suggests that Katniss loves Peeta, and not just because she feels that she owes him her life. Instead, Katniss wants to protect him and bring him home because she has strong feelings for him, even though she isn't sure what those feelings mean.
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.
Why would Johanna get Wiress and Beetee for Katniss?
Johanna asks what happened to Mags, and when Katniss tells her she says Mags was Finnick's mentor and half his family. She also explains that she saved Wiress and Beetee because Haymitch told her that if she and Katniss were going to be allies she had to save them for Katniss.
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."
The following year after Lucy Gray Baird's victory, another female tribute emerged as the Hunger Games winner. Mags Flanagan became the first victor from District 4, living off of nuts and her survival skills by creating fishhooks. She was also the first victor to move to Victor's Village before serving as a mentor.
Peeta used the dyes to paint a picture of Rue after Katniss covered her with flowers when she died. He says he wants to hold them accountable for killing Rue, and Effie tells him that that kind of thinking is forbidden. Katniss then tells the team she hung a dummy of Seneca Crane.
Chia Mags kisses Finnick on the mouth to briefly let him know that this is the last time she will see him. It's her way of saying "Goodbye" but in a more affectionate way.
Yes, Katniss did develop an addiction to the morphling, on account of constantly being sedated with it, however, I wouldn't say that she was an addict. An addict is someone who goes to a substance (or whatever their 'poison' may be) under their own mind.
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.
Katniss, drugged and recovering in District 13, dreams of Peeta. She wakes to find Johanna Mason stealing Katniss's morphling drip. Katniss had been spared serious injury thanks to Cinna's armored Mockingjay costume.
Peeta, Johanna, and possibly Annie were held in adjacent cells. As part of their torture, they were forced to listen to each other's screams. Johanna was starved, beaten, had her head shaven, and she was soaked with water and tortured with electric shocks. This caused her to develop a fear of water.
Their relationship was all friends. They trusted each other, but that doesn't mean they had romantic feelings for each other. Plus, Cinna's too old for Katniss.
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.
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.
