Well, apparently she is not a hard nut to crack, but I don't really see it as romance. She respects you and has sex with you but she is still rude and unpleasant. I don't have the impression you are done after the sex. It's not the actual endpoint.
Her approval is still only fair so basically, she is using you for sex.
I was surprised too, it happend like right at the Druid grove and not at the camp party. Apparently my new Fighter is irresisteble.
Maybe I could be satisfied with pinning it on githyanki culture or something, that sex doesn't equal romance, if that's accurate, lorewise (I have no clue).
But even if it's due to her respecting your protagonist, the respect should build slower than that. She gives off the impression of having high standards and being high maintenance, so that just seems to go against her character.
