Sam didn't know how to apologize
I have always sustained, and keep saying, that Sam is not and has never been abusive, or a walking red flag, or any of the things some people like to call her. She acted like a d*ck and messed up a lot, but I can't point out any time where she was being an asshole where you can tell her intention was to be hurtful. Sam was clearly not socially well adjusted, her grandma didn't let her be herself, her sister told her to pretend, and her friends just went with it. So in many instances she didn't know how to react to things or what to do.
As the episodes progress we can see her getting better at it, and in my opinion nowhere it is most obvious that in her apologies.
The first time that she messes up with Mon, she tries to make amends by just bringing her food, no words and no other actions.
Mon, being the self respecting person she is, is obviously is having none of that. After that fails, it's Kirk who ends up apologizing for her and bringing Mon for dinner.
The next time she needs to make amends it's with Jim. Initially she suggests to Mon that she's going to call her the next day, and this time is Mon herself that gently steers her in the right direction. She tells her that she needs to apologize in person, which she does.
When she goes to Jim, she starts by giving her snacks, which seems to be the only thing she knows what to do. And then, she tries doing the exact same thing Mon did with her.
Sam obviously tries to learn a lot about what to do in social situations from TV, so she ends up apologizing to Jim in a "Lakhorn" way.
Later in the episode, when Mon is mad at her and she doesn't know what to do, she googles it and the first answer is "sincerely apologize".
Sam discards this and tries a social media dance instead. When it doesn't work she tries apologizing and is actually surprised that it works.
So the next time, after some puppy play, she does exactly that.
After her outburst at the end of episode 8, she needs to apologize, hard. So she takes what she has learnt. She didn't call, and instead she went to Mon in person, and waited for her to give her the chance.
And then, again after some play, she sincerely apologized.
Honestly, the Khun Sam from episode 1 and the one from episode 12 are like completely different people. But I don't think anything showcases more her evolution than this. She is constantly trying to do better, even when she still messes up.