Levia is not a scientist performing experiments to create something, she's a researcher looking into Malice. That is not the same thing. Her area of research is specifically about souls. Furthermore, who would she be trying to create? It's a sketchy connection at best. We don't know that FML is Second Period, because we don't even know exactly what Irina's line meant by the song changing every era--It might not be "changes every time they move on to a new world" and might be "every time a significant amount of time passes". Like, "It used to be la la la lu lu lu but after Levianta fell it became lu li la". Keep in mind that the lullaby has also been distorted in other songs that were set in Evillious.
I'm sorry, but we have a song sung by Irina that explicitly quotes several lines from FML suggesting she is the one who said them originally, or at least has a connection them, and we still have people claiming it's more likely to be Levia because she wears a labcoat? At most, Irina is the Rin character (likely different Vocaloids because Iroha didn't exist when the songs were made). At worst, there is as much a chance of it being Irina as Levia.