Is Wadee ever mean to Hin?
Not intentionally at all.
Wadee isn't like Lukprae from Boy Next World, who felt like she was entitled to Cirrus, owned him, and could have what she wanted and claw the eyes out of whoever got in her way.
She just believes... Tul will be her husband one day. because that is what her mother has decided, it's a good match. Tul is polite to her. He has a visceral hatred of women because of what his Grandmother and Stepmother put him through, but he doesn't let Wadee ever see that. She isn't to blame.
If Wadee is dismissive of or a little rude to Hin, it's because she only sees him as a servant, nothing more. Her future husband's future assistant (what Hin was being raised to be). Just another servant in the house.
Tul was drunk when he had sex with Wadee, he had no idea she wasn't Hin, he was blackout drunk (luckily, though he wasn't gentle, he wasn't too rough either, just a bit rough for a virgin).
At some point after Phupha's birth, Wadee kind of gradually realizes Tul was in love with Hin, and she is probably what came between them. Wadee herself realizes what she has with Tul isn't love, but respect, after falling in love with a French man while on vacation.
Tul grants her her divorce, and after she marries the French man, they reunite for Phupha's birthday. Wadee reveals that she has figured out the relationship between Tul and Hin, and encourages him to go find his own love too.
But Tul won't, because he swore to Hin that he wouldn't look for him. And he would rather die alone than break another promise to Hin.
So Tin goes instead because NO ONE made Tin promise nothin'.
