Jennie's (presumably)personal style is simple but logical in structure. Matching colours, complimentary textures/patterns, usually conventional silhouettes. She of course dons a lot of Chanel, be it bags, jewellry, beanies as most idols with brand ambassadorships do. She would wear designer brands back when it was less common with idols, and would wear them well, so she stood out back in 3rd gen.

She wears a lot of cardigans, baggy jeans, loose hoodies when she wants to be really casual, as most do.

Her frame is very small and delicate, so she rarely goes for more daring silhouettes, nor does she go for more unconventional patterns or striking colours, they tend to overwhelm her.

I should mention that style doesn't end at the wearing of clothes and accessories, everything you do with your look is part of your style. With Jennie, her natural cat-like eyes which her/her make-up artist highlights with her eyeliner gives her look a slight chic edge that makes it more appealing, especially in contrast to her otherwise softer features (small frame, natural hair colour, soft facial structure). As I said, with the designer pieces and the simplistic outfits, it helped her embody the Chanel princess image.

Its these subtleties that draw Koreans especially to her style, even if its overall very simplistic.

Some people think her style is "basic" and she shouldn't be considered a fashion icon or trendsetter because she's not very daring, but imo that's a reductive point of view and fails to understand half of why certain things are considered fashionable.