I sometimes like to imagine Vader meeting Leia on the Tantive IV and wondering why in the hell she seems so familiar. He’s heard of her, sure, but since Vader is not always directly involved in politics he’s never seen her before and she’s just so young. But it’s not just that, there’s something else…
I think it also bothers Vader that she is completely unbothered by him. Vader is probably used to getting the upper hand on people purely based on his appearance - especially when you consider his suit, his height, and his modulated voice - but Leia is completely unfazed. She openly defies him, she lies to his face, and she’s smug about it, too. And yet, despite all the setbacks and confusion, Vader cannot for the life of him put a finger on why she bothers him so much.
Maybe it’s the way she talks to him, or her lack of fear, or maybe it’s the youthful veracity that tinges her every dissentful remark.
Once Leia escapes the Death Star, though, Vader finds himself preoccupied with the origins of another - a certain Luke Skywalker. Not only is he the pilot credited with destroying the superweapon, but he bears the same name as him, as well as the same tutor: Obi Wan.
Vader thinks nothing of Leia, at least not until his confrontation with Luke on the second Death Star. Luke’s origins are almost a no-brainer. Once he learns of the rebel’s surname, it’s only a matter of time before he confirms that the boy was his… but there was no mention of a sister. After all, Leia was an Organa - he always knew that. Regardless of whether he followed galactic politics or not, Bail Organa had been a contemporary of Padmé’s, and royals have kids all the time, right? There was no reason for him, or anyone else for that matter, to think otherwise. But suddenly, Leia makes sense to him now.
She looks like Padmé. She has her eyes, her hair, her same penchant for politics - but she’s not actually like her at all. She looks like her mother, yes, but she takes after him. She is as passionate and personable as Padmé, but she is fueled by the same fearless ferocity as Anakin. He sees Padmé, but all Vader can sense is himself - but a better self, an old self he left behind long, long ago. And in his son, he sees his older visage - the same youthful face framed by blonde hair, those bright blue eyes - but he senses Padmé. Luke has her kindness, her compassion, and her unending patience when it comes to others and seeing the good in them. Leia is tempestuous and argumentative, and just as impatient with the galaxy as Anakin was with the Jedi Council.
She has Padmé’s eyes, yes, but she is also every bit of Anakin, yet a far better version of himself than he could ever possibly be.