Hi Will,
There are a few adults with ADHD who post here from time to time.
Hopefully one of those will see your post and give you their thoughts.
My perspective is that of a close friend of an adult with severe ADHD and other conditions and also that of a parent of a now adult child who has executive dysfunction but was diagnosed with ADHD as a child. I believe that was an incorrect diagnosis. He certainly did have attention difficulties and was hyperactive, but he also is on autism spectrum and so I see his symptoms a little differently. I don't have ADHD myself. My adult friend gets through life just fine really but there are times when it has been very hard for him.
It's difficult to answer really without knowing if she's coping or not.
If she's not coping it would probably help her to know if she has ADHD or something else... e.g the executive dysfunction. I also wonder what she thinks would be the benefits of having an actual diagnosis. How would that actually benefit her do you think?
If she wants to work on her problematic areas then there are lots of resources available these days for her to do that. Are these things that are problematic to you and those around her also problematic to her?
There are lots of tips and tricks she could find to help her organize your life so that it runs more smoothly if that's what she's wanting.
Perhaps looking at her strengths might help her. Instead of concentrating on her problematic areas, turn it around and figure out all the positive aspects.
In my opinion that can help for so many of these conditions especially if the person is now an adult and some behaviours will be deeply entrenched. OCD for example. Apart from the many downsides to having obsessive compulsive behaviours, it's also important to remember that people also have their strengths and sometimes that can really work to their advantage especially in employment situations. Same with the ability to hyper focus as in your sister's situation.
Anyway, that's just a little from my perspective.
Below I've added a link to a site meant mainly for children but it does talk about adults as well. It contains a lot of information about different conditions but this page has a link to an "Overview of Executive Dysfunction"
http://www.tourettesyndrome.net/diso...e-dysfunction/
sorry the post is so long.