nanocas
The situation you describe in your post with your girl falls into the first catagory where the CC will help as you are trying to do your best (I am sure)
If you were the type parent who EXPECTED the crew to deal with it while you did nothing you would fall into the second.
And there lies the subtle difference
And just out of interest, what do you do to keep your little girl safe if she won't stay strapped in?
That interests me as well.
Another true story
Small turboprop operating into an airport with a shortish runway such that on landing the brakes had to be applied hard on.
Piece of equipment at the rear of the aircraft not secured properly.
Upon braking that piece of equipment travelled from the rear to the front down the aisle and smashed into the flight deck door damaging it, fortunately it did not injure any passengers.
If children are unsecured does anyone want to see a child do that?
Does anyone want that child to be injured or worse lose it's life?
Does anyone want another passenger (possibly another family member) injured?
Or should the aircraft keep circling the destination until the child can be persuaded to have their seatbelt on (bearing in mind that, at least in the UK) have to wear them in a car.
The leaning over the seat back & chattering to other pax I think is minor - if an adult can't switch off to that well......
Crying cos they are tired - not surprising all children up to a certain age do