It doesn't say how much time, if any, was given. The lady implies she wasn't give any chance. Usually it takes me just a couple minutes of walking around, getting the kid interested in the "pretty lights" or some other diversion. I know strapping them in a seat "right this minute" generally is not the answer.
Well of course she does... she wants everyone to think this was unfair. On the other hands, flight attendants fly kids every day, they don't eject good customers from flights lightly or they'd be out of business. If we can assume they are at all reasonable, I think more than a few minutes passed.
I think this flight was to fly home..I wouldn't be surprised to find out the "darling" was throwing a fit because they where going home...that changes my perception of the problem..my kids only cried when the air pressure would hurt their ears.
Althought the article doesn't say for sure, I would imagine that the parents and the child had been on board for time enought to do what you suggest. I would think that up until the time the flight crew approached the parents they had been busy getting the other passengers settled into their seats. A process which can take some time