When I was younger, I was friends with and sort of dated a "smelly" girl but she was a pretty normal girl, just had some medical and other issues that made her smell kinda bad a minority of the time. She felt kind of insecure about it and got some bullying over it but it wasn't that big a deal

But when guys online talk about "smelly girls" its usually some sort of fetish where they dont want them to bathe for a week or something