Greetings. I believe I had selective mutism as a kid. I believe it was caused by my extreme social anxiety, which I still do have. I was just diagnosed with ASD. I know selective mutism is the most common with social anxiety and separation anxiety. And ASD I believe is most common with intellectual disability (not Aspergers, since the criteria excludes this), AD/HD, social anxiety, etc.. The list of co-morbids for ASD is very long.

Anyways, as a kid, I wouldn't want to talk to anyone. I would whisper if I had too, but never talk normally. My teachers expressed this as a problem, but my parents didn't do anything since I was very social at home. Maybe you should start with something like picture cards? Like, with some basic things on it like "yes" or "no" or something. That way, she could start communicating. Maybe this way, she'd feel more comfortable in starting to talk. I believe I sit next to someone in my class with selective mutism. She barely talks and will only whisper when she does. But I'm unsure, since I'm not a professional.

Hope this helps [emoji3].