Ah, but you see, this is exactly WHY it would make sense to sell it.
Think about this: She knows the actress was underage. Seeing as how strong she feels about it morally, WOULD she sell the videos if it was anyone other than her?
If it's her, she could easily see that by selling it, it's victimless now, as the victim, is profiting off of it. She has won back control, in a way.
It mirrors how a lot of rape victims will act out to win back their sexuality and sexual freedom. They feel it was stolen from them, so they do things to steal it back.
This could easily be what Maki is doing.
I don't think Maki is bad enough of a person to sell CSAM of someone other than herself; and seeing as she knows all the history behind the series, she is obviously aware of exactly what it is.
But again, if it is her? She would still have the moral high ground to sell it. It would make sense for her to use it to confront Akira as well.