Purdah between non-mahram males and females

Q: My friend [24f] makes parda from her brother in law [17m]. However her father's first cousins is her husbands maternal uncles and she doesn't make parda from them. Upon telling her she brought the hadith of brother in law being death and said there is no specific ahadith relating to her having to making parda from her husbands mothers brothers therefore she doesn't have to. Is it true?