Well, Otome isnt exclusively straight, is it?
As for why the story MC fell in love with our MC, no doubt she is bi.
While that is rare, it happen in this timeline
I'm pretty sure the way Lapis-sama caressed Natori could no longer consider as treating her like a child, though. Not like I'm gonna complain about it. I hope Natori would one day realize that her 'ba-dump' was not a 'ba-dump' from a job well done but something else.