Man, don't get me wrong... I had to laugh at that whole YouTube thing. So, does it all come down to YouTube? I mean, I usually make a "family-friendly" version of a module just to avoid issues when posting it there. It’s a hassle, isn't it?
Like I said, if he picks a subtitle that hasn't been used on any other media, everything should be fine.
Regarding MK content on YouTube, the big issue is the music—and that applies to anything MK-related, not just the games.
If you ran into trouble with MK content beyond the music, then you were just unlucky, because plenty of people post MK gameplay there and monetize it normally. Obviously, the content gets flagged as mature-only. Maybe your mistake was trying to publish the video for all ages.
Yeah... Anyway, after all these years... ZVitor probably just lost interest in MK. Copyright issues like that really kill a creator's motivation.
Your friend could publish the good stuff she made here, or on sites like itch or gamejolt.