you're onto something here
I also thought about that, either she's a spirit of a goddess of something (like maybe the author themselves manipulating peoples feelings or maybe some god), or it's actually the spirit or soul of the past yuri. My guess is that Yuri was obviously so sick of the same ending she's getting (it's like the way i see it she's stuck in an infinite loop of her ending being a helpless fl to the ml's). That maybe Melissa's reincarnation triggered it causing all of the novel's timeline and plot to suddenly change.
That what I was thinking but I won't be surprised if Melissa is like fuck off
I think so too
the reasoning why the mls are suddenly changing for the better, and the ghost silhouette at the end of the chapter, I think that the spirit who's sticking to Yuri, telling Yuri to do main character shit and stuff, is now gonna stick around with Melissa, because she is a potential main character (in which she is!) which was why the mls suddenly acted differently than usual and showing more affections to Melissa. It's because the spirit is controlling them. possibly maybe lol? just a theory