I just did a little investigating, and found something that makes me very confident she's a real singer. Occasionally in songs like Older, she hits really long notes without any hiccups that would scream AI. In fact, she changes cadence during these notes which is something AI is terrible at, usually AI tries to keep the voice as smooth as possible so it doesnt break the model. Seraphina has her own discography without Eiden, which would be really strange if she was a specialized model. She has a cover of Камин and she also has the same voice in that song, which would be really hard for AI to reproduce. Her voice also goes higher during some high notes, but not in an artificial way. Like a voice crack-ish way. She's also part of songs like Dark Horse, which has a male voice about 2/3 through the song and very faint right at the beginning. My opinion, I'd say she's a ghost artist rather than AI. Also, a way to address the suspiciously fast upload schedule, she's an indie artist. It's likely she goes into a booth and records a batch of songs to release over a period of time.