I've gone back and forth on Squall and Rinoa's relationship over the years. I've always liked Squall, and for a while I was worried about what I saw as Rinoa's efforts to change him.
It took me a while to realise that Rinoa wasn't trying to change who Squall was. She was trying to persuade him to interact more with the world: to change an aspect of his behaviour and outlook, not of his personality. By the end of the game, Squall is still Squall; he's still the quiet, introverted, serious young man we've come to know. He's just more willing to ask for help when he needs it, and to let other people into his life.
Rinoa doesn't want to shape Squall into some romantic ideal; she likes him as he is. But she wants to help him make connections with other people, because, even if Squall's isolation helps him to avoid being hurt by loss, he's not happy.
It can be hard to make positive changes to your life when you're on your own. Sometimes you need other people to encourage you, to be by your side, to draw you out into the world when all you'd do otherwise is mope in your room.
I've written elsewhere on this site about how, as a teenager, I was very similar to Squall. For me, the other people who helped me open up were the friends I made in secondary school. Some of my closest friends to this day are people who annoyed me slightly at first, because I was so closed-off and hard to connect with that you had to be slightly annoying to get to know me. You need to be determined if you're going to befriend someone who doesn't know how to have friends. Fortunately for Squall, Rinoa is very determined.
I think Rinoa is a really positive force in Squall's life. I think their relationship could work either as a friendship or as a romance; I slightly prefer the idea of the two of them as friends, because their romantic chemistry doesn't quite click for me, although that's just a personal thing. But, in either case, I think it's good for Squall to know this playful, friendly, positive person who's always willing to reach out to him.
On a final note, the ballroom scene is one of my favourite cutscenes from any videogame ever made. Squall's terrible dancing is a delight.