Jin is the greenest of green flags
From when we meet her, it’s clear (to everyone apart from Zuko) she has a crush on Zuko. She acts on this confidently asking him out and not waiting for him to make the first move. When they meet, she immediately tries to establish physical contact by embracing him and playfully messing with his hair.
During their dinner, despite the awkwardness, she is eager to understand Zuko’s story, asking open-ended questions not to interrogate him but to tear down his walls. She does this by being enthusiastic and showing interest in everything Zuko says. Most importantly though she is not being judgmental at all; even when Zuko fails to juggle, she doesn’t get suspicious or criticize him.
Then it’s her turn to be vulnerable. She wants to show him around her world, and reveal a place important to her; hence her disappointment when the lights aren’t lit. I think that’s why she doesn’t get suspicious of Zuko lighting the lights; it doesn’t matter to her how he did it, but that he did it to be in her world.
Finally, when they lean on for a kiss, she understands Zuko’s awkwardness and isn’t put off by it. Instead, she remains kind, comments on Uncle Iroh’s wisdom, and tries again, this time with a more delicate approach.
In the end, I think that's why despite only 4 mins of screen time, their short story feels so impactful; she is the one that got away. After all even Zuko, at this point in the story, was able to admit "it was nice".