Correct Answer: Try to calm her down

Solution : Let's check each option according to the given statement –
First option: Tell her how to avoid mistakes.
The situation at hand involves a passenger who is currently experiencing distress due to a mix-up with her train ticket reservation. We must address the root cause of the problem and seek a resolution, rather than simply providing advice on how to prevent similar mistakes in the future.
Second option: Tell her how you booked your ticket.
The current situation pertains to a passenger who is grappling with a mix-up in her train ticket reservation, causing her considerable distress. We must identify and tackle the underlying cause of this problem, rather than simply offering generic advice on booking a train ticket.
Third option: Try to calm her down.
A distressed passenger aboard a train is experiencing significant emotional turmoil due to an unfortunate error in her train ticket reservation. Our first course of action should be to provide her with comfort and reassurance, allowing her to regain a sense of calm and composure so that we can work together to find a solution to her predicament.
Fourth option: Get irritated with her.
It is important to remember that in a challenging situation, it is not productive to become annoyed with an individual who may be experiencing difficulty. Instead, we should prioritize finding a solution to the issue at hand and ensuring that the individual can proceed with their journey without encountering any additional inconvenience or discomfort.

Hence, the third option is correct.