Yeah it sounds like severe PTSD, and those anxieties come from very real negative encounters. The problem of the dysfunction is that you start to view every interaction as the same. Stuttering for me, especially on the worse days, feels like someone is pulling a veil over me. That veil lingers until I can decompress after being alone for several hours. Since she developed her stuttering through an injury rather than development I can only imagine it could actually be a stronger PTSD response. I imagine going from a fluent speaker to having a stutter is more traumatic since you can readily understand how you are treated differently. As some whose stuttering heavily fluctuates between severe to mild as an adult, I am always shocked at how differently people view me. When it is severe I get treated as someone who is mentally handicapped, even when people are being kind/understanding. It isnt their fault as they are trying to understand something they rarely encounter. It really messes with your sense of identity since we are an extremely social species. Since stuttering is a non visible disability we are unfairly disregarded and our trauma gets minimized. It further messes with one's identity being gaslight that it is "all in our heads." It's never been as easy as "don't care what others think" when our worst fear isn't death itself but abandonment/being ostracized (which for hunter gatherers is a death sentence). I'd love to instantly stop caring what others thought but it turns how others view me is essential for my well being and quality of life. Personally I think that stuttering is a dysfunction of the brain and it's awareness of when being observed. I have a wierd thing of never being able to feel comfortable if I know I am being observed or if there is a potential of it in a space/ We have all of the hardware to certainly be fluent speakers, something goes haywire beyond our control nuerologically. When interacting with another verbally different parts of the brain are activated, stutterers do not stutter when they sing because a different part of the brain is responisble for that then just with verbal conversation. It's the same reason why we do not stutter in our thoughts or when writing in any format.