Well I couldn't disagree more with some aspects of what what most posters seem to be saying. This is for a number of reasons, the first of which is that you've stated the teacher compared your DD to the rest of her class, whereas her tutor compared her to a national standard.
OP please read this thread www.mumsnet.com/Talk/primary/2219583-Ability-levels to see the view of a respected teacher from this site, mrz, regarding comparing children to others in their class and why this is poor practice.
Secondly you didn't mention dyslexia, you said "dyslexia with numbers". The term for this is dyscalcula. It was the teacher that took your expression and ran with dyslexia rather than understanding what you meant by 'dyslexia with numbers'. I knew and I'm only a parent.
At the end of reception your DD's report stated that she had met the relevant expectations, at the start of yr 1 she was moved down a book band and you hired a tutor. Given that teachers and parents regularly post on here that plenty of children often start yr 1 on pink / red band I am surprised no one's given this more thought. What band is your DD on because unless it's lilac non-word books she could still be at the bottom end of normal, which is not the same as behind?
Thirdly the tutor did not criticise the teacher - she said she didn't understand the teachers assessment and she didn't think dyslexia should have been mentioned. Well perhaps that's because 6 is still too young to make the diagnosis because reading 'just clicking' can happen in yr 2 & even 3 - this is mentioned on MN threads all the time.
What I am interested to know is, if your DD doesn't respond, at all, to any adult at school, how exactly has she been assessed? No data or missing data doesn't equate to being behind. I'm not saying she isn't behind, just that there's an obvious logic issue here.
I really hope you get in touch with a support group for selective mutism because you are going to need to be your DDs advocate if this is her issue and the school lack understanding in this area.
It takes very little time to include positive comments which are all the more important when delivering worrying news to a parent - a poor bedside manner is no longer acceptable for GPs, why is it acceptable for a teacher?
None of my views are critical regarding the teacher putting in place interventions, which is also something the OP clarified - the issues for the OP are the delivery, the mismatch between two professional view points and the lack of engagement regarding possible selective mutism. I hope I've understood correctly OP? And
for you and your DD and apologies for the length of my post - it is a foible I'm afraid!