Don't try to parse the language used by a random GA or FA. They are not testifying in court under oath, simply conveying the fact that the flight is delayed. Whether the FA in question was abducted by an alien spaceship or became ill, timed out, got in an accident enroute to the airport or any number of other things is irrelevant and also not the type of information which is any of the GA's business, so she likely did not know.

Of course UA has FA's on standby at EWR, but not that many and not at 01:00. If they have 2 and a third one is needed, callout is the only option.

Everybody gets bad press here and there, but ask yourself whether, if you were the crew scheduler and making a presentation to the Board, you could make the business case to pay crews to standby for every eventuality. Same thing with aircraft. There are backups, but only so many.