It could be either. Sometimes people make up such stories for entertainment or to shock others. But it might also be a true account of an unusual neighborly encounter.
It could be about a neighbor who has a very flamboyant or inappropriate way of dressing and behaving that the author finds both off - putting (nasty) and in some way alluring (sexy).
No. Nasty sexy stories usually contain sexual or inappropriate content which is not suitable for all audiences, especially children and those who are sensitive to such content.
In modern society, we strive for equality, respect and positive cultural influence. Sexy nasty stories go against these values as they may objectify people or promote unwholesome ideas. So, they are not acceptable.
We should avoid using such terms as they contribute to slut - shaming. Instead, we could talk about stories of people having healthy, consensual and positive sexual experiences without using disrespectful language.
Be cautious about the sources you visit. Don't go to websites or platforms that are known for adult or inappropriate content. Also, be careful with social media, as sometimes such stories can be shared there. If you see something suspicious, don't click on it. And educate yourself about what is appropriate and inappropriate content so you can easily recognize and avoid 'nasty sexy stories'.