Quick Transmigration: The Millennia-Old Supporting Character Strikes Back

She transmigrated by accident, and the System gave her countless supporting-female-lead roles! Accept them, and she'll be tortured to death by the male and female leads! Refuse, and she'll die on the spot, reduced to ashes. So she gave in. With a supporting-female-lead script in hand, she traveled through one world after another, laying countless obstacles in the path of each story's leading couple! Who could have guessed that the supporting male lead who appeared out of nowhere would be so handsome he stole her heart? So she promptly tossed the script aside and started dating him. System: “Hey, hey, don't forget your mission!” Supporting Female Lead: “I have only one mission: win over the rich, handsome villainous male lead!” Male Lead: “You don't need to win me over. I'll come snuggle up to you myself!” System: “...”