I am a speech-language pathologist in a public school, and I am working with a 7 year old boy in second grade who has selective mutism. He has not spoken to any adults in school since his entry into kindergarten, and only began speaking to children late in his kindergarten year. He speaks freely and quite well at home, according to parent reports. Interesting to note that his older brother has a similar history, and did not speak outside of the home until he was second grade age.
I do not claim to be an expert in this area, but I base my intervention on years of experience working with kids, knowledge of behavior modification techniques, and understanding of this disturbance.
This child began receiving speech therapy this year. I work with him using the theory and techniques of Applied Behavior Analysis, and so far so good. These techniques include shaping behaviors, fading prompts, and generous reinforcement systems for requested behaviors.
I feel that the most important thing for me to do is establish a trusting relationship with this child. He needs to know that I mean what I say and that I will follow through. I have stressed to him that I understand how difficult it is for him to think about using his voice around adults, and that I'm not worried about it, as long as he COMMUNICATES in some way. We have discussed using head nodding/shaking, pointing, gesturing, and are now considering employing a picture communication system for him.
Because Selective Mutism is an anxiety disorder, I personally feel that stressing the importance of communication (not necessarily speaking), and conveying acceptance of any and all communicative attempts, coupled with the development of trust in an adult are key to effective treatment. We are still trying to deal with the issue of the other children communicating for him. We are involving his whole class in his treatment.
While it is frustrating for parents, teachers and other adults involved, imagine the feelings of fear and anxiety these little kids are experiencing!!
Good luck with your silent girl. You might consider consulting with a behavior specialist and speech-language pathologist for help.