She was put into a new situation with new people its understandable for her to feel a little alone in a crowded room at first. Eventually she will feel less lonely and make new friends. It will be sink or swim in the end for sure though.
Sid is going to have to convince Kaia that he loves her just as she is and would never want her to change!!! At the same time she's got to learn to operate in his world too:)
I don't think 5 years is too much in their situation. Where they have both been competively almost only living for the sport(s) for how long. That to me would be the hardest thing to navigate in their relationship but they both already acknowledge it and understand it themselves. In every day life a 22 and 27 to me depends on their situations. There is a lot of life experiences during those years that people can form bonds over if that makes sense. It's a situational thing more often than not. IF they both want the same thing out of the relationship and know where they both stand in each others lives they it shouldn't be a problem