selecive mutism, anxiety in daughter

Hi there

My daughter who is 5 has always struggled socially with other children. She has been in school since age 3 but still does not talk to any of the other children. We expect she will soon be on the pathway to diagnosis as teachers agree she has ALN (autism and suspected ADHD - as well as selective mutism). In school she presents as very anxious and does not talk to other children, but does now talk to familiar adults (teaching assistants mostly). She has not even seemed to mind not being able to talk to other children, but is now occasionally saying she doesn't know what to say to them, and that she has no friends, which is upsetting.

She is taken to a few extra curricular activities outside school where she really enjoys herself, seems more at ease (with parent accompaying her) but still only talks to the adults and not with the children at all. 

I am really starting to worry about her as she seems to have low self esteem, she is also highly sensitive in that she feels rejection strongly. At home she is very controlling and needs constant one to one attention, which is difficult as she has a younger brother. I think she is showing signs of PDA also - she cannot abide being told 'no', and she must be right at all times and cannot be corrected without getting very frustrated.

Unfortunately we don't meet up with friends with children very much as we don't live close to them. I sometimes wonder if it might have been easier for her if we had friends that we meet up with frequently, but I find meeting up with friends difficult anyway as my daughter really resists any kind of socialising.

I am finding it hard to know how to help has as I am also autistic .I also recognise that I have also suffered with selective mutism myself which I have never had help with.

She doesn't have particularly strong interests but she does love sensory activities and being outdoors.

Not really sure what I'm looking for but any advice or experience particularly with girls with selective mutism, would be great. Has anyone got any experience of therapies with SM? What has helped?

Thank you X