Princess of convenient plot devices

"After reincarnating into her favorite BL novel, Maki (now Octavia) has the perfect opportunity to fangirl over her favorite fictional couple, Sil and Prince Sirius, in real life--except she's Sirius's sister?! If that isn't awkward enough, she's ecpected to give up her firstborn child to be their heir! But the new Octavia won't settle for a political marriage just to produce a baby, Her brother overcame many obstacles to be with the man of his dreams,...