Becuase any woman present in a BL that doesnt follow the 'big sister' trope always gets lodged in as a villain. They are also usually very poorly written which can make them seem more annoying/irritating to the reader. Women being poorly written in BLs is unsurprising considering its a male centered story!!
Then again, it would be nice to see a change in this trope every now and then tho
Shes not annoying she literally got in the worst situation getting scammed and played by a playboy. How would you feel in her situation? Obviously she holds a grudge
Not really limited to BL. Most shojo manga/manhwa have this trope where the female rival is a freaking "beach" that every reader what to kill. Even in Drama, it's so freaking common. But I agree with you, it's annoying. It wouldn't be that bad if most of them could have a proper background and not just shallow shell to make the MC shine "brigther".
Why all girls in yaois have to be annoying