Before this gets misinterpreted, he's referring to Adult Maria still using Young Maria's voice. Can anything be done about that?
Yes. With
Tinke (maybe Pemburu knows about it, but if he doesn't, then here is my suggestion). You can extract and reinsert all sound effects used by the game, meaning that if you get your hands on Adult Maria's SFX, you can replace Young Maria's. Nothing will break as long as the file is more or less the same size as the original (NEVER bigger, or the extra space will move stuff around and break everything).
And yes, it works. I've already done it to laugh my ass off at Dracula uttering memes to summon his moves.