Since the end of "Mirror. Mirror" established her presence on the prime universe Enterprise, I was wondering if the character had made any appearances in Trek Lit. I can't remember any offhand. Maybe Marlena is so strongly identifed with the Mirror Universe that no author ever included her in a prime universe tale.
http://memory-beta.wikia.com/wiki/Marlena_Moreau Doesn't seem she's been used, but the episode itself establishes her as a new arrival, so lots of TOS novels set before "Mirror, Mirror" don't include her.
I'm kind of surprised that no one has done anything with her. I would think the fact that we she plays such a big role in the Mirror Universe would make people more interested in her Prime Universe counterpart.
I'd certainly like to see more done with her after reading Sorrows of Empire. Surprised she hasn't turned up before in something. Seems like an easy character to use for quick nods, as she has virtually no background.