I don't mean to presume that my experience would be helpful to you, but I'll share it just in case. My DD was never diagnosed with SM, and she doesn't have any issue with it now at the age of 8. She used to be mute for at least an hour when brought to new places, or even in familiar places that were hectic (like preschool).
I believe there was a turning point for her when she made her first friend, which was another shy, gifted girl. Perhaps you could create pressure-free opportunities for a friendship to spark, involving the type of person with whom a friendship would be plausible.
For my daughter, that would exclude anyone who would:
Introduce themselves to her.
Appear to want anything from her.
Raise his/her voice (even in excitement).
