In my mind, she was never really human. Mind over matter, yes, but there is a biological/medical component too. I don't think you can 'mind over matter' a change in your DNA. So, it had to be temporary. And, yes, I agree the thing about her WANTING to be human for a man and child is totally out of character for her. I do understand the writers giving 'happiness' and then taking it away since vampires can't be rewarded for their murderous and evil ways, especially to a vampire who actually ENJOYED being a vampire.

Also, in my mind, Janette is either dead (fire kills humans and vampires) or ran away just before the entire house was engulfed but after Nick left and has stayed away for whatever reason. I also think Nick did not attempt to bring her back. She was pretty clear she didn't want that. They show Nick with his head thrown back, fangs down. I didn't take that as he was preparing to bite her but the same grief reaction that Janette had when her man was shot. Same position, same facial expression.

I also think that if Janette didn't die, SHE killed the men who set the fire.

The only thing that doesn't jive with that theory is Lacroix's comment about 'losing a daughter and regaining a son'. I don't know how that fits, no matter what theory you subscribe to. How would Janette dead fit with that? How would Nick turning Janette back onto a vampire and then abandoning her fit? Unless he meant that he knew NICK had killed the men who set the fire (Nick acted like the vampire Lacroix wants him to be). But then, why, would Nick seem so surprised when he arrived to the crime scene, looking around for 'someone'. Did Nick think Lacroix did it? Did Nick think Janette was lurking someplace? He looked a mess when he arrived at the crime scene, as if grieving/shocky. Why would he grieve if he knew Janette was alive?

So, I'm kinda with you about 'someone make it make sense'.