I don't think so, though it's true she can be dense when it comes to herself. She's often awkward type, just like her brother - we've seen her first contact with Yamada. She probably doesn't realize, that with age she's got less awkward simply by not being basement-dwelling kind of incel, but outgoing one who has many same-gender friends, band, and part-time work, and that again, with age, people around are also older and more likely to start looking behind first impressions and appreciate your less-obvious merits and virtues. She's dependable older-sister type, but teenage boys probably didn't appreciate that, especially when she was mostly studying instead of going out with other kids, and her lack of high-school experience probably killed her university years chances. Maybe there was a guy or two who were into her, but with her feeling of general social failure she missed them, but I doubt ti was that many.
Kana is now mostly in female company, well she knows the band of older guys who definitely aren't going for her, she doesn't know any guys at uni because she considers that time a failure of socializing with boys, so I doubt she has that many secret admirers - probably she just now starts to make people be really into her. Let's say she's like fine wine, that can be appreciated by true connoisseurs.