I suspect my niece has adhd...

and I've been suspecting for a while. The niece is almost 9.Her mom who is primary caregive is really struggling cause she almost never does what she was asked to do. She stuggles at school from what i've seen in her teacher's notes. Higiene is hard a bit and her room becomes a mess in seconds literally. Her mom is really overwhelmed because of that. She has outbursts which I get but my niece told me she is dumb which is extremely heartbreaking. I don't think they would be happy me even implying that she might be atypical. What should I do? How would you approach this?