When the comic was out, there were a few interviews with both Mantra (not easy, considering she's a fictional character), as well as her creator, Mike Barr. Here are some of the stories I've been able to track down:
"The Magic of Mantra"
An interview with Mike Barr from just before the series started. Some interesting insights into the character and the man who created her.
"Mantra: The Hero Interview"
An interview with Mantra by Hero Illustrated, obviously during an early point in her career.
"Prime: The Hero Interview"
An interview with Prime by Al Baker (the fictional scourge of the Ultraverse publishing world), as published in Hero Illustrated. Contains a couple of cute comments about Mantra.
A two-page layout of (ahem) "Mantra" in ULTRA-Monthly as arranged by Al Baker. Why let a little thing like the truth get in the way of a good story?
"Fury Like A Woman Scorned"
Al Baker goes over the top with his account of his encounter with Mantra. (Who apparently wasn't too flattered by his earlier story.)