From the 2017 novel, Thrawn by Timothy Zahn.
In the excerpt above, it clearly states: “…All the brushstroke spoke to him; all the light curves told the story of their creator”.
Thrawn only knew of Sabine Wren from Imperial records and criminal reports. Most Imperial Databank reports on her were rap sheets of her misdeeds as a Rebel. They did not get at the heart of who she was and in order to tear her a part “piece by piece”, he had to meet her in person, or as he discovered that Sabine creates — ART — his favorite and greatest passion.
By the time Thrawn got to Sabine Wren’s graffiti art, there was much more to her than just her mere brushstrokes on her “canvas” or chosen lighting. It was rebellious because it was graffiti. But she was using it as an outlet for her anger. No different than him analyzing art. She did not do these for commissions, or cultural moralities based on her chosen color for their forms. She creates her art for performances to fight — which enthralls him, completely.
What is more interesting, Thrawn did a cursory study on Mandalorians (possibly before he left The Unknown Regions) and learned all the Mandalorian Houses and Clans. When he discovered that Sabine Wren is a Mandalorian, he became perplexed about how many Mandalorians are “artists”.
It is perplexing when Thrawn studies Sabine’s art for all the deeper meanings.
Her art shows line and color control with her “brush nozzles” to relay art in nature for functional design.
Then Sabine sends Thrawn a “message”.
Apparently, Thrawn interpreted this message in a manner Sabine had not considered — that the mighty Grand Admiral Thrawn would reciprocate her message as a “crush”. In a huge galaxy, what would be the likelihood of two people meeting and sharing an appreciation for art?
Then he had to tell Colonel Yularen about Sabine’s artwork to throw off any Imperial Intelligence of his crush. He does it in Star Wars Rebels: “Through Imperial Eyes”.
Then in Star Wars Rebels Season 4 Finale, Grand Admiral Thrawn “outs” Sabine Wren as if she was “not what he wanted” but only her art to Ezra Bridger. Ezra saw right through it and his voice rises and he tells Thrawn he does not deserve this art in terse terms. Exchange the term “art” in that sentence for “Sabine”. Thrawn takes it and tells Ezra it is not what he wants, but who has power. Thrawn knew he had no power over Ezra, given that he has the Force, and therefore brought him to the Emperor.
The subtext to this scene is that Thrawn’s eyes widening as his voice breaks when he begs Ezra Bridger to take Sabine Wren’s art that Thrawn feels is a part of her as he destroys the planet she is on, Lothal. Thrawn wanted to meet Sabine before destroying her, which suggests that Thrawn desired her and could get it, if he truly wanted it.
Watch Thrawn’s eyes when he speaks of Sabine. They widen and then his voice breaks. This scene also shows one of the rare times Thrawn becomes emotional to humans. Chiss do not share emotions even among each other. Passionate expressions in Chiss society are seen as rude, maladjusted and unhealthy. Since Chiss are adults by 10 years of age, they have had military training (flash training perhaps) where they are well-practiced in emotional separation and they problem solve logically.
In Legend Canon, Thrawn does have an issue with controlling his emotions among the Chiss, but not among humans. Humans tend to accept that kind of behavior as normal. This issue may be part of the reason why Thrawn feels comfortable in the presence of humans, even when they are emotional. While as an alien, he cannot become more emotional than humans, he can maintain composure. He has to maintain his composure moreso among the Chiss. His struggles with emotional control are not a character flaw directly.
Art is Thrawn’s character flaw. As it is his emotional outlet where he can focus his anger, rage, hurt, pain and all his emotional passions upon his analysis. But what about love, compassion and care — the good feeling emotions? Where do those go in his analysis?
Sabine Wren creates her art to for that purpose, the good emotional feelings and support, so that she can heal. What if Thrawn started to see the “good emotions” in Sabine’s art and fell in love that by his analysis, which inadvertently caused him to fall in love with her, first as a crush?
As for Sabine Wren, she has NO IDEA until our fan-fiction that Thrawn has those kinds of feeling for her. She finds out from Minister Hydan, one of the Emperor’s lackeys, that Thrawn has a collection of her art. She brushes off with a tsk and says, “tell him I’m flattered.” while she rolls her eyes and crosses her arms. It appears she is more annoyed that she got caught by Hydan than her introspective thoughts on why Thrawn has her art, or better yet, why was she told about it. What has he done to her artwork in his collection. Perhaps, it is all a lie, because she only paints to rebel and relieve stress.
The relationship in Star Wars Rebels between Grand Admiral Thrawn and Sabine Wren seems to be hidden in off the cuff comments Thrawn makes. In one instance, does Sabine Wren ask about Thrawn (season 3) and it is only in reference to pre-planning battle tactics. It is easy to see she is not thinking about him.
But for Thrawn, what he has learned about Sabine Wren and how his comments about her several times as shown above causes him to order the Mandalorian Tyber Saxon to find Sabine Wren and make her fix the weapon she crafted for the Empire long ago (the Duchess) and left the Empire because of its destruction.
It all comes down to Thrawn has a huge crush on Sabine Wren.