booking ticket  

Do not worry about. The ticket agency tried to push your friend to book tickets from them.
as you said your friend had not paid yet, so it means the tickets are not sold by airlines. the agency might just book it in their system and they have not paid to the airlines yet. so there is no cost to them. They said they will do legal action on your friend it's just their way to warn customer or cheat customer.
Your friend can check on website of the airlines to search if his information already in the system or not, or just call the airlines telephone to ask if his booking done or not.
I suppose they can find the truth. Also if your friend ignore the agency the agency would not bother him again. They are busy with their business and would have no time to have legal action with one case. The cost would be more than they can get, not to mention they will lose on the court.

Welcome to wonderful My Lot. I suggest that when booking airline ticket and at the some time get travel insurance. When booking a ticket on the phone it wouldn't be sorted unless a debit or credit card detail had been given. Good luck to your friend.

As you said they booked it first though the phone through a travel agency; that means that your friend did give her INFO to that agency and if the ticked was ordered through the phone then yes they have to pay it probely unless they have an insurence to cancel it...