Oscar could remind Ruby of her importance in the fight against Salem. He could tell her that she is the one who gives hope to others. And Qrow could share some of his own wisdom gained from years of being a huntsman. He might put his hand on Ruby's shoulder and say that crying is a sign of strength, not weakness, and that she'll get through whatever is making her sad.
Blake could share her own experiences of dealing with difficult emotions. Since Blake has a complex past, she can empathize with Ruby on a deeper level. She might hold Ruby's hand and tell her that it's okay to feel sad. Jaune could be a bit clumsy in his attempt but his sincerity would shine through. He might crack a few jokes at first to lighten the mood and then offer some words of encouragement.
One possible reason could be the loss of a teammate. In the dangerous world of RWBY, if one of her close friends were to be seriously injured or die, it would be devastating for Ruby. Another reason might be the pressure she feels as a leader. She has to make tough decisions and carry the weight of her team's success or failure, which could become overwhelming at times.
He might crack a joke. Ron has a knack for using humor in tough situations. Something silly to make her laugh and forget her troubles for a moment.
The other members of Team RWBY would be deeply affected. They would start to question their own abilities and the purpose of their fight. Some might withdraw into themselves, like a broken Weiss who shuts out the world for a while. Yang, on the other hand, could become reckless in her pursuit of vengeance, endangering herself and others. Blake would try to hold the team together, but she would also be mourning privately. The other friends and allies in the RWBY universe would also be in mourning. Qrow might blame himself for not being there to protect Ruby, and Ozpin would see it as a great setback in the fight against evil.
With Weiss, their relationship could be more strained at first. Since Weiss has some preconceived notions about Faunus, she might be initially distrustful of Ruby. But as time goes on, they could overcome this. With Blake, they might bond more deeply as they both share the Faunus experience in a way. And with Yang, Yang would be very protective of Ruby, especially if Ruby faced any discrimination because of being a Faunus.
If Ruby has a new identity, Weiss might initially be suspicious. Since they have a complex relationship, Weiss could think Ruby is up to something. But as the story unfolds, Weiss might see the good in Ruby's new identity and their bond could strengthen in a different way.
Chase might use his police skills to cheer her up. He could 'arrest' her sadness by making a little game out of it. He'd say something like 'You're under arrest for being too sad, Skye! Now you have to laugh.' Rubble could offer her one of his favorite building blocks as a present. He knows sharing his precious things can make others feel better.
Ruby's relationship with Ozpin could be really complex. Ozpin has a lot of knowledge about the world and the Grimm. He might see Ruby as both a threat and an opportunity. He could try to keep an eye on her, which Ruby might not like. As for the rest of Team RWBY, they would all have to adjust. They might worry about Ruby losing control and hurting them or others. But Ruby's loyalty and their shared experiences could help them get through it. Ruby would have to work hard to show them that she's still the same Ruby they know and love, just with a different side to her.
Ruby would become more confident. As a queen, she has to make important decisions, and this would force her to trust her instincts more. She'd also grow in terms of her leadership skills, learning how to delegate tasks and manage different personalities.
Weiss would probably be very protective at first. She has always had a bit of a mother - hen side to her, and seeing Ruby in a more vulnerable, deaged state would bring that out. She would likely try to keep Ruby out of trouble and make sure she was taking care of herself.
On the other hand, it could cause some strain. If Ruby's magic is unpredictable, it might accidentally put her team in danger. This could lead to some arguments and tense moments as they try to figure out how to deal with this new aspect of Ruby. But through communication and training, they would eventually learn to work with her magic and grow even stronger as a team.