hey hey! I write betrayal scenes like my life depends on it. It's a main conflict between my two characters as well, and I have spent a lot of time trying to perfect them, so I now present: Shea's Step-by-Step Guide On Making Characters Hate Each Other and Making Readers Hate You!
Step 1: Give them a reason to feel betrayed
good news! you've already got this step down! It's always easy to figure out once you realize you want a betrayal scene. So, reason for betrayal: Protagonist refuses to return with character A.
Step 2: The Confrontation
The moment when one character realizes the offending issue. This would be when Character A discovers Protagonist can conjure rain. This should be emotional, like the betrayal itself is already happening. Anger, tears, maybe some early accusations ("why didn't you tell me??" type beat). This is my favorite part to write, because you can capture every early thought almost immediately.
Step 3: Retaliation
When the other character fights back against the accusations. Whether it's gentle ("please, I didn't know") or angry ("you think I knew about this??"), it has to have the same impact as the confrontation. Not necessarily the same emotion, as the person retaliating can be keeping a cool, level head. However, they should attempt to make the other character see their point of view, and make the readers sympathize with how they see it. It has to make people start to root for them.
Step 4: The Rebuttals
This can go on as long as you want (although not too long). This is the part where the two characters are arguing back and forth about this. This is the buildup to the bomb dropping. You want some tension, maybe some pacing around or throwing arms out wildly as they attempt to explain. ("I can't believe you didn't tell me!" "I thought we were best friends!" "I tried explaining, but you didn't listen." etc.) Basically, just give the characters some time to really let the tension build and give the readers some time to figure out who they want to root for.
Step 5: The Bomb Drop
This is your big moment. The climax of this scene. Maybe it's a scathing sentence worded exactly where one character knows it's going to hurt the other to hear (maybe something like "it's your fault!" when one character has been blaming themselves for a past problem) or an actual physical action, like a slap. This should be the peak of this scene. It should make your readers gasp, cover their mouths with their hands, throw the book across the room while screaming "NO!". It should hurt.
Step 6: Realization
We've all seen it. After a character lashes out at another, they soon realize what they've done and run off before anything else can happen. I'm trying to think of examples, but I honestly can't, because it happens so. much. This should be when everything is winding down from the climax, immediately after the bomb drop. This should also be emotional, but less explosive. More tears and stammered apologies than top-of-your-lungs red-faced screaming. Characters most likely separate from this point on, for any period of time (a few minutes, hours, a couple of days–my characters don't talk to each other for 5 years after their conflict. It all depends). After this, you have a couple options, but the two most popular are:
A. Forgiveness
or
B. Revenge
And you can take any path you want on either! Remember, this is just a basic guideline and you do not have to follow anything I say. I'm literally just a random person spewing words into a shoddy old Chromebook that hardly works anymore. But regardless, you can always let me know if you have any other questions. Hope this helps and happy writing!