Good, one, Teresa! Thanks for the imaginary dialogue.
If I recall correctly, the family fell in love with Hae-in when they saw her pictures on his cellphone! They had known he had a girlfriend, then Da-jung borrowed his phone and found the pictures, and she showed them around to the rest of the family. They were all over the moon about her from the word go. It was quite ridiculous. Thereafter, it was always, "Haein is so pretty, and she looks like she has nice manners, and I just KNOW we're going to be Bestest Friends Forever! If I had to die a slow, painful death starting tomorrow, I would still be ecstatic and grateful just knowing that she is Ki-woong's girlfriend, etc. . . "