If I mischaracterize Jude and Fio, I'm really sorry, I will fix it, just let me know. I'm not sure how they would interact with Xipil and Milo, so it's how Xipil and Milo would interact with them. It's also pretty lengthy, so I'm sorry.
Fio + Jude
For Step one, Xipil is terrified to talk to Fio and Jude. But then again, she's like this with everyone. Very nervously, she will compliment Fio and then overthink and believe she upset Fio. Xipil always has some geodes on hand, and will offer it to both of them. This is how she asks to be someone's friend, and she will not be upset if you don't take it. If you do, she will visibly brighten up and smile. If Fio becomes her friend, Xipil will always bring her any gem she wants. For Milo, he might be offended Step one. But he'll respect her space and give a friendly wave. He will leave her alone and go off to do his own thing. He'll offer her a shell and/or a shark tooth. He'll ask if he can be her friend, then will do his best to keep quiet. Xipil will always offer her jacket since she can stand the cold, so if they need another layer, she doesn't, mind.
For Step Two, Xipil will be polite and try to not mistake any interactions. She'll try to be friendly, but will back off if Fio tells her to. If they're friends, Xipil won't question why Fio is kinder to her since she is the same way. Xipil completely understands Jude, so she won't question it. Both Xipil and Milo will offer advice for Jude. But Xipil will always have back up stuff ready in case Fio or Jude ever need another pencil or pen. Xipil always packs extra snacks too (she does this because this is how she shows she cares). She is also a great listener and will not interrupt them. If they're friends, Milo will note their favorite colors and preferences, so that when he makes bracelets, he knows how to do it right. If they don't want any, he'll ask if she has any design ideas.
In Step Three, Xipil is more confident and outgoing. She'll be polite and kind to Fio, and wouldn't judge her (she does not pay attention). She'll talk to her, but it'll be more off a general kindness. But if they are friends, Xipil will makes tons of jokes. For Jude, she'd probably spend some quiet time and draw a bit. If Fio or Jude ever ask, Xipil will make one for them. Xipil will also offer to drive Fio and Jude to any location (if they want to). Xipil will wait, and will most likely be shopping while she waits. She is also the friend (for both Jude and Fio) who will ask for a wrong order to be made correct (only if they want her to). Milo, if they're friends, he will pay for any food or drinks. He doesn't want his friends to worry about being unable to afford it, so it's always free with him. He'll goof off with them, and he still continues to make jewelry. He will give her some if she ever asks. She'll often offer knowledge about rocks and geology to them, and Milo offers marine knowledge.