I would argue that there doesn't need to be a fixed amount of chapters for a backstory to be revealed but the important part is the approach.
Like dropping bits and pieces every couple chapters and having a somewhat boring story if you take out those elements, that's what's making this feel like it drags on.
If this had a larger overarching plot or working towards it or the author took time to built their world instead of writing comedy into the dialogue, this would be fine.
I remember reading "Tower of God", it was only after 50+ chapters that a huge plot twist was revealed (the betrayal of a certain someone).
But it worked because the rest of the chapters were engaging, the world felt vast and the
side characters didn't feel empty next to the Mc.
This Manhwa basically has nothing if you take out the Mc, it feels empty and those hints at her backstory don't make for a good substitute as a plot.
its honestly taking way too long to reveal her backstory, if it doesnt get reveal in the next few chapters i just gonna drop this for a bit. i feel like the max amount of chapters it should take for a mc to reveal their backstory is 20 chaps especially when its extremely relevant to the plot. the creator couldve gotten away w making her backstory a plot twist if it wasnt so obvious that some of the characters are mixed up in her past, like revealing bits and pieces of her past without knowing who the specific characters are, then slowly introducing them. but it feels like its dragging now because we know that her past has so much to do with whats going on w her.