Autism isn't ADD/ADHD/dysgraphia/dyslexia/dyspraxia/dyscalculia. But 75% of autistic people also have one of the latter, and families with clusters of the latter are also far more likely to have autistic members, too. They are linked disorders.
The diagnostic threshold for one of the disorders is that it is significant enough that it's an impairment. If it isn't, you aren't diagnosable. We all have traits of the above disorders, because they are part of the human condition. But if they don't disable, then you don't have the label. They are, by definition, disabilities. ADD isn't just being a little absent minded, and autism isn't just being very good at maths with a little social awkwardness on the side.
I have ADD. I am not autistic. Autism is a discrete diagnosis. My brother and son are autistic, my father has ADD, my mother has dyscalculia, a cousin is dyslexic and has children I think are ASD and ADHD respectively and my toddler girl is suspected of ADHD. My husband has ASD traits and his father is blatantly well over the diagnostic threshold; he's only without one because he is 72. Various of these linked disabilities are all over the family.
I second the comment that finding out that your child is disabled is akin to grief. I was very aware that it was his diagnosis, and very uncomfortable with some mothers who seemed to make their child's diagnosis their identity (I had no idea, at the time, how consuming securing the necessary support is, and the lengths people will go to to avoid providing it...). I found the neuro-diversity movement, as your friend seems to have done, and it was a huge comfort to me as well. I liked the fact I was asking autistic people how best to help my son - it seemed far more respectful than solely asking other mothers, when we weren't the ones directly affected. And I was so encouraged by the argument that autism isn't a disability, but a different way of being. It was so much what I wanted to hear. It was only when I read an article by an autistic woman who expressed her frustration with what she described as the fetishising of brain damage that I started to reconsider. Because while there are some benefits with my own child, he is impaired, and substantially so. His life is harder. It will always be harder. And pretending it isn't doesn't make that go away.
It's true that autism does confer some gifts in some cases, and so does ADD - again, IN SOME CASES. It's not the magical creativity fairy bestowing golden gifts, but when your mind is constantly buzzing with thoughts and you seem to lack a reliable record button in your memory in the way other people do, and distraction is your... oh look, an earwig! then you sometimes develop something called hyper-focus. This is an extraordinarily intense capacity for concentration; the ability to target a subject with laser precision and focus so wholly that nothing and nobody else penetrates until you're done. It can mean some people with ADD are hugely successful academically, or at a sport, even if they can't pass a driving test. Autistic people (and some people with the linked issues) often have areas of special interest, with which they are wholly obsessed. Anyone wholly obsessed with an area, who spends endless hours focusing upon it, will become expert. If the area is one of general usefulness, then suddenly that person has a desirable skill. I suspect, too, though this is my own observation of two very different kids, that if you aren't that interested in a lot of things people usually are, and if you miss a lot of the emotional and social games people play, then you have a lot more time, energy and focus to dedicate to say, lego. Which is endlessly diverse while remaining wholly logical and predictable. And this may mean you end up with a startling capacity to think and design in three dimensions with all sorts of media, and with an enhanced STEM abilities, because you've done a lot less of the usual early years interests. Narrowing can mean specialising.
I don't think autism is a blessing. My son first said he wanted to kill himself at the age of five. His life is a hard one. And I can't tell you the extent to which I hate and resent my own ADD - it feels like the evil fairy at the christening, frankly, because I come from a very academic family and was successful academically myself, but I can't organise my own housework on any sort of consistent basis. It's frustrating to a level I can't describe.
But if this mother is using neuro-diversity as a life-raft right now, then that's what she needs to do, and my heart goes out to her.