Fortnite has a habit of alluding to things before they're revealed. The other characters seem to think Lexa is hiding something.
@SweetRabbit posted two pictures on Twitter that show two potential bodyguards being very suspicious of Lexa. They tell her that she's hiding something and that she has darkness in her. This could be a way for Fortnite to set up some future storyline.
While some may have just seen what the characters said and ignored it, many replies have given out their own ideas of what may be happening. It's gone from speculation on what Lexa is wearing, to what the bodyguards say, to other crazy theories.
Epic Games does not just add a new feature without reason. In video games, nothing is coincidental. Every inch that a character moves is intentionally done by an animator, every word is written out by a writer, and every placement is made by a level designer. All three work together to make a cohesive story, and Fortnite has been known to make little references towards the same.
Fortnite made great allusions before revealing anything in Chapter 1
All of a sudden, in Season 3 of Chapter 1, there was a meteor in the sky. At different points on the map, there were telescopes that all pointed to Tilted Towers and this was alluding to how Chapter 1 would eventually end.
Fortnite is very good at making fans speculate in advance with little clues and hints, and this may be happening again.
Just looking at the replies to the tweet shows how much attention this kind of theory has received, and that's normally what Epic Games wants. Her description literally is, "Don't let her cute face fool you," so there has been an intention for her from the start. It'll be interesting to see what she will end up doing, but the clues are already there.