Well that does happen in real life also. The golden child of the family. Some takes it to the extreme like the story but others might not be that extreme.
About them all falling in love with her, I can't explain that part
"How could they prefer one daughter over the other? " trust me, it's such a common thing irl too. Also, it's crazy but many people don't even have a sense of kinship towards their family. Sometimes your non families treats you better than someone with the same blood running on their veins. Shtty people truly exists
If you think somebody needs a reason to be hated, then you're wrong. There are many people who hates someone so badly over random sht or no reason at all
The story is really dry and understandable how could a whole family fall in love with a single person while her birth family didn't? Like she isn't even an illegitimate child or step daughter or like she made her mother dies in childbirth or something? How could they prefer one daughter over the other ?