In England what the school is saying is nonsense.
If they can see that she is struggling eg with social communication they should get a Speech and Language therapist in and get some advice about how to help her eg small group social skills training, or whatever seems right to you.
If they can see that she is struggling with attention, then they should be making sure that she has instructions broken down into shorter bursts, and that she has resources sent home, or whatever would help her to keep up.
The law says 'special educational needs must be met'. It does NOT say 'only special educational needs which also attract a diagnosis must be met'
If you are England the you can apply for an EHCP which might result in assessments by an educational psychologist, school, your input, any relevant medics and any relevant social services (possibly not relevant to you).
IPSEA is a great place to start reading up
And lots of support on these boards