When Rumi met Mira she had absolutely no idea how kids their age acted around each other or what friends interactions looks like. So when Mira, being the neglected and angry kid she was, saw this supposed Nepo baby that looked and talk as if she was above her (she was just being weird because all she knew was Celine and that woman can't be any good at social clues. Also it's my personal head canon that Céline is as autistic as Rumi and that's why her autistic traits went totally unoticed to the woman) and just started to be bitchy with her.
And Rumi picked up on it thinking that must be how kids her age interact with each other and started to be bitchy toward Mira too cause she actually liked her and wanted to be her friend. But that only made Mira act bitchier with her.
Then Zoey came into the picture. Sweet, kind and full of energy. Both girl instantly took a liking to her. She was bright and still a little mischievous. Mira immediately decided she was going to be her partner in crime, her fellow troublemaker.
And Rumi, well she really wanted Zoey to like her too, so she did what she did with Mira. Except Zoey's reaction to it was not the same and she couldn't understand what was wrong. What was she doing wrong.
Zoey was used to bullies and kids being mean to her so she knew how to act like it didn't bother her, even if it actually hurt. She thought that by joining huntrix she'd finally found real friends, and she did with Mira who was so cool in her eyes, but she couldn't help being disappointed about Rumi. She could still see some good in her, sometimes when she let her guard down she was actually pretty nice to be around but it would always end with a mean comment.
All while Rumi tried everything to be liked by Zoey so she started to be meaner and meaner thinking that it would work at some point, until one day she went to far and hurt Zoey who ended up crying. Then Mira exploded on Rumi yelling at her and asking why did she have to be so mean. Only to be shocked by the tears, confusion et guilt on Rumi's face.
"I just wanted her to like me."
"By being a bitch to her !?"
"I just did what we did. I just wanted to be her friend."
That's when Mira realised that Rumi was only being bitchy because she was to her first and that this girl had no sense of what friendship is like. She had figured out after some time that Rumi spend most of her life isolated but she was too blinded by her annoyance to make the connection. She knew she fucked up on that one and she needed to make things right.
After a long discussion between them they made up and Rumi tried to be more herself while Mira promised to be less mean (and silently vowed to herself to always protect them), and Zoey to be more open and tell them when things went too far.
After that they became inseparable.
