I think she knows he's a human??
I mean till now we still don't know how she knows Iruma, she seemed determined to protect him since the very first time they met, you can't just meet a stranger and go "i'll protect him and even betray my group and boss for him"
She seems to love him so much yet he only came to the demon world just recently
And she even betrayed her group for him
I thought she knew iruma is a human way back then at the amusement park arc
That's what i thought too, that's the only conclusion i could come up with
Im still 50/50 with Shida if she would protect Iruma once demon world found out that hes a human and be in danger. Though she said (non verbatim and not sure what chapter) that she won't let anyone harm come to iruma..