I would strongly advise, and you would certainly have nothing to lose, by logging your disappointment in the autism 'assessment' with PALS. If you can, then quote professionals who have seen autism traits in your daughter, and in particular the ADHD team who are now refusing to medicate her until she has had an assessment for autism. And be very clear that the lack of a proper assessment (e.g. ADOS) means that the ADHD team are no longer able to treat her. I went to PALS with less evidence than this, and managed to secure an ADOS assessment. If this fails you could also go to your GP and ask for an autism assessment under clinical partners 'right to choose'.
However, an autism diagnosis in and of itself is probably not going to help you or your daughter for the current situation she is in. It is possible for children who have both autism and ADHD to be medicated (for ADHD), so after the assessment, there is no reason not to have your daughter back under the ADHD team with a change either to the dose or the medication itself. Apart from that, a diagnosis will give you and her some validation and perhaps a shorthand in needing to explain her needs, but the diagnosis itself is usually the end of the road in terms of the medical journey, as autism is not something that is in any way 'treated'.
I assume you have already looked at the many different ways that autism presents itself. It should, in theory, be in the EHCP, but if not, look at ways you and the school can support her particular unique set of needs, regardless of any diagnosis. There is no 'one size fits all'. I'd recommend following Autism Inclusivity on Facebook.
It does sound like she would probably benefit from a more specialist school, and there are many types available, depending on the needs of the child. Start documenting the ways in which the school is not meeting your daughter's needs so that you have a case for moving her to a setting that is more accommodating of her needs. I assume the school are currently saying that they can 'meet need'. If they really can't then you need to point that out to them, as the school admitting that they can't meet need is another important step in securing a specialist setting.
As suggested upthread, also get a thorough assessment of need done via the adoption support fund. This may lead to some sensory integration therapy, play therapy or other therapy, but see what the assessment throws up.
I really feel for you. There is so much in your OP that feels so contradictory. Not in the way that you've written it, but in the sense of lack of joined up services literally sending you round in circles.
Good luck. I wish it wasn't such a battle getting proper support in place. This is where we are with SEN provision, though. Keep speaking up for your daughter. One thing I have learned is that staying quiet will not get you anywhere.