At the risk of sounds indelicate you came on here to find a way to have them "not get away with it" and the Etihad rep gave you a contact and asked you to send the relevant info.
It was then followed up with a general apology. Do you want them to insincerely apologize or do you want them to look into the situation, find out where things went wrong, fix it and also apologize to your mother for what happened.
Talk to the company and let them correct the failure. We'd all like it if everything went perfectly all the time but things happen. They can't fix them if they're not told and they can't make it right by your mother without looking into them.