i think you mis-understand controlled crying...
when a baby (typically one who has never settled themself) crys because they dont want to be in bed...
you go in and calm them from 'crying their eyes out' to just sobbing amd leave..... each time you take longer to go in.... and ONLY go in when they are crying their eyes out... NOT just sobbing...
generally you would give it at LEAST 5 minutes anyway....
so that fact that this child was asleep 10 mins later meant she wasnt exactlty crying for long... (and was probably only sobbing after 5 mins, so you wouldnt go in any way even if you were doing controlled crying (which she wasnt))
nanny did NOT do controlled crying.... which would involve repeatedly calming a very upset child to a sobbing one..... but left a child who seemed to be playing up to sort themsleves out.... rather than "playing games" when its night / bed time
She did NOT practise controlled crying at all!
Agree with others.... if you cant stand the thought of them crying a bit then look after them yourself! (personally i wouldnt look after children who werent 'allowed' to cry... they have to learn, and you do have to be cruel to be kind... if they learn that crying gets their own way it leads to spoilt children who just cry to get what they want... because for them crying "works")
the fact that she was later ill is neitehr here nor there.... nanny is NOT psychic and cant be expected to be either!