I noticed that you didn't answer if she was part of the discussion that DH has to tell you the details about their sex life. If not then DH saying he doesn't feel comfortable about that might (and probably is) because he talked to her about that and SHE isn't comfortable with her sex life being discussed with you.
Why does your want of hearing about it override her need of having that privacy?
Woodsmith: My husband
Merry: Tig's wife/slave
N8: Merry's boyfriend/owner
Elle: N8 girlfriend
Ruby: Part of the Leather Family
Logan: Leather Sir in the Family
Arc: Logan's boy
Holly: Leather family
K: Holly's sub