@midas-queen asked: “How would you make a subtle transition from a character hating someone to loving ‘em so much they can’t live without them? Not necessarily in a romantic way.”
Hate is such a strong emotion. If your characters are going to hate each other, they most likely will try to avoid each other for the most part which is not particularly helpful for building a relationship. But there are things that can help force a change.
Like forcing them to spend time together. Like sticking two high school enemies together to bond over a school project. You’ve got to find a way to make them work together to move past hating each other and towards benevolence. It doesn’t actually always mean requiring them to team up, but having some shared interest or drive can help bring them together.
Another example, if your character hates her sister-in-law, the reason for trying to change the relationship might be her husband. He might be uncomfortable around both of them together because of his relationship with both of them. In this case, the husband might talk to his sister about his wife and to his wife about his sister and they may be able to get to know each other through him. This might further make them want to work out their issues.
There has to be some will to work together or communicate to cause the relationship to change. This is true for building out any kind of relationship that starts off negatively.
As far as a relationship amping up from casual friend to “can’t live without them,” is going to take some bonding and probably some kind of intense emotional experience. I don’t know about you, but my best friends often aren’t my best friends until we’ve delved into some deep emotional messes. It’s in part about being able to open up to someone for one thing. There needs to be that level of comfort there.