Like you said, it doesn't have anything associated with it other than its plain meaning, so why associated it with housewife? The only attributes here are Married > no chance with her; and Woman > older, more mature than others.
If the nickname was just supposed to be beauty, kindness, and elegance, it would be something like Big Sister, or Princess, or something along those lines. If the nickname was just supposed to be about someone out of their league, it would be something like Unattainable Flower or Idol, etc.
This is how she is introduced in the ln
Kasumi in particular was also known throughout the school by the name ”Cougar.” It wasn’t
exactly the most normal name to give a high-school student, and nobody would fault someone
for questioning the mental sanity of whoever thought it up. However, it also made sense in a
way. Kasumi looked mature for her age, with her eyes and lips possessing a peculiar charm to
them. She was tall, had a figure that would make a model jealous, and was also quite... well
endowed, to say the least.
For better or worse, Kasumi’s features were more akin to that of an adult woman rather than
your typical teenage girl, especially with how she radiated allure.
The nickname suits her to a tee, all things considered, Soukichi thought. Obviously, Kasumi wasn’t
exactly keen on it herself. But whatever the case, she was pretty much the equivalent of a school
celebrity. Despite her glamorous nature, her modesty and social skills managed to win the
admiration of everyone who came in contact with her, regardless of gender.
This might be really rude of me, but I never would’ve thought that someone as outgoing and
sociable as her would have a hobby as mundane as reading, he murmured to himself as he realized
that he had let stereotypes dictate his initial impression.
In any case, Kasumi did indeed fancy herself a bit of a bookworm. She enjoyed all sorts of
novella: general literature, light novels, character-driven novels, and belles-lettres. She loved
anything that came in a novel format, and it even extended as far as anime and manga at times.
In other words, she was a big fan of fiction and especially stories.
Either way, as Soukichi took some curious looks at Kasumi, he appeared somewhat dejected.
If he himself was a self-described “loner,” then Kasumi would be a textbook example of the social
butterfly archetype. She was always upbeat, friendly with just about anyone, had lots of friends,
and, above all else, was both beautiful and elegant in appearance.
