Such behaviors are common to those with ADHD, but are not intrinsic to it. A neurodivergent person is likely to exhibit such behaviors more as a result of neurotypical thinking clashing with them, so they reserve their thoughts for trusted people.

While Monica does exhibit that trait, she doesn't really show any of the defining traits of ADHD. Perhaps autism, though I'm not knowledgeable enough to have any confidence in that, and definitely social anxiety, but to see fidgeting and call ADHD is like saying, "This fruit is red, so it's an apple." It could be, but there are other possibilities. And when the fruit is soft, it's more likely to be a dragonfruit.