It's because the manhwa is making her seem like a heroine, if you compare to appearance of other female characters. The way the novel and manhwa portrayed her is different.
what are the difference bet the manhwa and novel ver of her?
Based on many manga and manhwa I've read the manhwa ver. of Jesse looks like those ditzy-pretty girl type heroine.
The Jesse in the novel is a person who is archmage class who only uses "skills" based on the player system not real magic as a discipline. Her interest in MC is stemmed from his real "magic" not using "skills" so her personality is childish-curiosity and passion for magic. Manhwa doesn't feel like that, she just looks like she's annoying MC and appealing to her looks acting cute to be given an answer rather than an oblivious character who only has magic in mind being persistent not knowing their a nuisance.
The problem is Jesse's excessive appearance than her role should be.
Honestly people are just immediately judging her on the spot. She seems like an okay character so far, it seems her current feelings towards our MC is just admiration and eagerness to learn.