Nah, the Shiro / Aina thing wasn't really that developed. The whole infatuation was far too quick and shallow. They met like twice and spent a few hours together and then they're suddenly in love and all.
I disagree. I saw it more as a chance scenario that blossomed into love. These were two soldiers who thought the other side were enemies & evil, but through working together to save each other's lives, something unexpected happened. It didn't just happen overnight, cause both of them were still focused on their own side of the war, but Shiro still thought about her even despite knowing that the chances of seeing her again were slim to none, especially considering that she was a Zeon soldier. Through twist of fate, they did meet again, and then realized they had feelings for one another, but even so they had to part once again. All it took was that second encounter to make Shiro question his involvement in the Federation, and made him realize how much he cared for Aina. When you meet the right person, a lot of times all it takes is 1 or 2 meetings. It's similar to Romeo & Juliet.
To me, the story of Shiro and Aina is the truest telling of a romance story, that being one of chance. That's what love & finding the right person really is all about. It's about chance encounters. I honestly thought Domon & Rain would wind up together from the very beginning of G Gundam. But with Shiro & Aina, going into the series blind, I didn't know. One could've wound up killing the other, or one could've died saving the other, or they both could've been killed.