You know Thie isn't that innocent as we think she is 
and the reason Dad is mean to her
and the reason Dad is mean to her
Spoiler!
He was a little mean to her because Astier intentionally provoked her dad by raising Agavert's rank to #1 too fast. It was also her plan to literally 'cut off dad's source of livelihood' by seigeing a lot of mana stones. This was so Tessetan would come to where Astier at (Agavert & Trevaga's HQ is neighbors in the capital) so she could officially meet him. Of course Tessetan got mad. Tie also knows based on dad's stories that being #1 is important to his dad so except the misunderstanding on the port, starting on raising Agavert's rank, every provocation was intentional. (Trevaga was hunting at Northern area. Tie initially wanted to go there but she was advised not to by the members + Luminen because the Order is there so it's very dangerous).
About their very first meeting at the harbor, Astier made a bad impression on Tessetan because of a misunderstanding. He got affected & genuinely worried for the kid he saw that was crying, calling him dad on the docks but when he learned it was Agavert's leader, he assumed an old guy was playing tricks with his mind and making fun of him. There were also plenty of rumors going on cementing the idea that Astier is an old guy. Like "he loves alcohol that he visits a tavern early in the morning until night". In reality, she's just acting and hiding the fact that she's going to kindergarten through a secret passageway under the Tavern.
I like to post spoilers for the stories I find interesting because I don't have much time to read novel due to busy schedule
you will find me in most romantic historical manhwa comment sections 
you will find me in most romantic historical manhwa comment sections 