So how did the prince got her blood to make the new curse, I hear you ask. You saw her vomit blood at least twice, yes?
How did he keep her blood from going rancid?
And if you think that's stupid, no one's crazy enough to keep blood as a souvenir... Google blood vial pendant. Apparently people do wear their significant other's blood as a necklace irl. Angelina Jolie used to wear one too apparently.
The world is a strange place.
The fight between Fiona and Matthias actually lasted a bit longer, and luke did have difficulty on removing the curse normally before he whipped that necklace out reluctantly. Mangaka was saving pages to shove in the ss in this vol.