I, too, have a similar issue. Mine is “v” sounds and “th” sounds and “f” sounds. Mine is also only associated with one person, my mother. I went through cognitive behavioral therapy for two years, talked to a therapist once a week, and am prescribed Prozac to help. These things slightly reduced symptoms…but nothing significant. I have heard mixed reviews on exposure therapy, too, although I’ve never tried that. This may sound strange, but I always keep a worry stone in my pocket. I pull it out to occupy my physical body and focus my mind when I get angry at the noises she makes while speaking. It’s a distraction. Hope this helped.