As your DD is recently diagnosed, you are probably still in the searching for information stage yourself.
A lot of traits of ASC and ADHD overlap, so reading about both conditions can only help you as a parent.
Additude mag online is a good resource if you've not found it already.
I like Purple Ella on youtube, she describes what it's like being an autistic mum to autistic children.
Sensory Processing is prevalent in both ASC and ADHD, this booklet's useful www.falkirk.gov.uk/services/social-care/disabilities/docs/young-people/Making%20Sense%20of%20Sensory%20Behaviour.pdf?
This is a great sensory resource with a section on executive function www.theottoolbox.com/
What's not mentioned enough is that many neurodiverse kids have an emotional age about two thirds of their chronological age and that needs to be taken into account when anyone says "At her age she should be able to ..."
my brother and his wife are always telling me she should
Be prepared for a lot of this, from friends family and even some teachers and medics who should know better, but unfortunately don't.
They know nothing about ASC or ADHD otherwise they wouldn't be saying those things.
It's up to you how you want to react to them spouting crap.
It would benefit you to grow a thicker skin and ignore them as much as you can. I have really tried to educate some people close to us, sent them links, even bought them books so they can learn about my DD's conditions and understand, but I may as well have saved my breath and pocket. They are simply not interested in learning or understanding, all they want me to do is follow their suggestions so she'll seem exactly like her peers.
I think it's very similar to the mindset of other idiots who "don't believe" in food allergies and put known allergens in peoples' food.
Here are a selection of replies for you to use, do paraphrase by all means.
You are assuming she's neurotypical, despite knowing that her medical diagnoses show she's neurodiverse, so no, your suggestions won't work.
'That doesn't work for someone who has ASC and ADHD.
That suggestion directly contradicts what her Paediatrician (or other medic involved) has told us. Thanks but we'll follow the medical advice.
Say these in your head if you need to after they make more inane comments.
No, she doesn't LOOK disabled, there again you don't LOOK stupid.
I see your PHD in Fuckwittery is showing again
Congratulations, you've just won the Star Prize for Today's Most Asinine Remark.