She isn't dense...just way too much cautious (who aren't when their live is in danger?!?)! In addition, the situation where she is, isn't at all clear, there are many (if not too many) "unspoken" things that help to make misunderstandings.
╮(￣▽￣)╭
I mean it makes sense to me at least. Like she's guarded against them and they're always speaking in vague terms. Not speaking out right like "I want YOU to do THIS" but instead indirectly giving hints that she's just misreading so really I wouldn't fault her.
It's actually the opposite. She is too clever to the point that she misunderstood it all!!
Clue after clue keep making her thought that there's something happened and that she's worried about her life.
I gotta say that this webtoon has a great list of misunderstanding event and yet it is so cute that we keep waiting for what kind of misunderstanding else she will make. The frustration for waiting when will the misunderstanding clear, and the sneak peek of happiness when she slowly getting to know each other. And a third wheel that's not actually a third wheel. Plus, all of the things she did is actually realistic when we take a time to think about it. Everyone would be overthinking in this kind of situation, right? The "Fuck of love, I want to live!" situation (〜￣△￣)〜
All in all, we should already nominate this FL girl is a Queen of Misunderstanding!
It is true that she is very intelligent, I fully agree with you!! (づ￣ ³￣)づ
Seriously, how dense can you get lady.