Time has a valid point. Any person should be aware when their passport is valid/close to expiry. It is too late really when you are booking a flight or checking in! I know not everyone uses email, maybe if an automated reminder went out 2 months prior to expiry date, I don't know if that is possible or currently exists. I am glad it all worked out for the sister in the end anyway.
Passports last 10 years so the expiry date is not the sort of thing that you would be aware of.
In my past experience I have found the passport office to be excellent.