It's a reincarnation or transmigration manga to a novel where the female mc is a side character or friend of the female protagonist.

It is complete!

The characters have lived the book numerous times over and over, but this is only found out near the end.

When the book comes to an end (story's climax), the world begins to as well but there is a battle and the female lead prevents this and the characters can live their own lives NOT tied to the story. There might have been some higher power, like a narrator who was the one behind trying to keep them tied to the original story.

It kind of reminded me of Kill a Villainess, I'm not sure but the female mc might have ended up with a knight.

Please help! I've been looking for it with no luck 🙁

Reminds me of Beware the Villainess!
https://www.mangaupdates.com/series/favu771/beware-the-villainess

I think this is also kinda count as a spoiler or something, but, maybe its ; I'm the Soldier's Ex-Girlfriend