It doesn't hold any water, considering Michele Specht of all people denied it in this Yahoo answer. Also had some stuff to say about rumours.
I read on a forum that Vic Mignogna was voicing a character from a particular anime (don't recall the name of it) with Mari Iijima and Vic said something about Mari's deceased friend who had committed suicide. Apparently, he claimed that Mari's friend was in hell for committing an unforgivable...
answers.yahoo.com
I could find literally nothing about Mari saying it herself. Sure, some people claim that she said it on some commentary to the anime Macross, but no links to any videos of it or the DVD itself maybe.
Here's a forum post about it. This person claims however that Vic simply asked her if she was close to the deceased actor, possibly without even knowing he's dead. Miles away from:"He killed himself so he's burning in hell".
On Anime and Manga - Other Titles, a GameFAQs message board topic titled "Has Vic Mignonga ever destroyed a panel of his by turning it into a religious..." - Page 6.
gamefaqs.gamespot.com
Excuse me for not being able to highlight the specific post on the forum, am on mobile. Just search "Mari".