The way the scar is described, makes it seem like it's a recent one, or only a couple of years old, when in the story it's actually implied that it's actually much older, over a decade old.

Now, third degree burns, at the age of event, covering that much area, would've been fatal, so, while we must be dealing with some third degree burns, they cannot be as extensive as implied. Our MC would've died!

Second degree burn scars fade to the point of visible discolouration, with slight ridging. This description is based on my own second degree burn, that I got as a teenager, and is currently no more than a curious blip on my skin. It's definitely not still red, nor swollen (although it did stay like that for years), after almost 20 years. (I actually have many burn scars... mostly due clumsiness XD)

Third degree burns also fade into discolouration, although the damage stays virtually permanent (since the skin melts, it's not pretty), especially in the most affected areas, however neither do they stay red for that long.

According to the characterisation, she should yes have a scar, but not as visible, ironically, the cover art makes a better job of depicting the scar, as the outer edges should be barely visible and only the most damaged areas should be obvious to a casual observer.

Like what? Hot honey water? Dude? Sir? Not to mention that she described his thingaling as being "almost as big as her forearm." No way she'd survive that, pretty sure miss is going to end up injured once I go to the next chapter. Lol. I lost it when he kept referring to her "mouth" as a hot spring. My goodness it was comedic.