What was her reason to confront Jasmine when she was offered to back down gracefully? She was not going to take chances with leaving an Anathema close to her hometown.
I'd rather not have her motive for staying reduced to a love story.
Jewel is a mercenary. She will leave eventually. What happens to our oath when she does?
Eh. Let me start with: I agree with you. Honestly. All you peeps talking about how suddenly claiming that Jewel is our primary motivation is abrupt/problematic/more-than-a-little-unwise make sense.
It totally is, Aster knows Jewel for how long? A few months tops. Arguably, possibly, probably, this is not more than an adolescent crush of someone who has a looooooooong life ahead of her and who will meet other girls that, as an added benefit, wouldn't consider her very existence to be, well, an anathema to the established world order and everything that is good and proper.
Which is exactly why I'm picking this option.
I think the interpretation of being a Solar Exalt that I like the most is being a legendary hero in Greek sense. They rarely luck out and live to an old age. Their lives are unending struggle full of triumphs but also hubris and vainglory. They feel strongly and indulge strongly in their emotions. More or less, being a Solar is being the main character in a classical honest-to-Unconquered-Sun tragedy.
And what's more tragic than unrequited love for someone who hates your very existence? Now, you can say it's unhealthy, but hey, a lot of things in Exalted are.
Also, about creepiness factor. It's only creepy if we stalk her, lol. Like, there's actually a somewhat altruistic motivation you can get out of it without making it about "winning Jewel over" or some shit. There's a Lunar terrorist targeting the city. The city Jewel is under employ of. She has demonstrated that she will not run from a fight with Lunars, she already marked herself as a Dragon Exalt who will oppose Winter Jasmine, so her life is unequivocally in danger.
And Aster wouldn't like someone who she has a very gay crush on to die, right?
It's not a very good motivation, in the grand scheme of things, but I think it's an acceptable one.