Just like her memorial tributes, this final sensual sendoff was part of her sealing him to eternity before her final act of exorcism. It's almost as if she was living some paranormal fantasy film.
This part I disagree with, Jodie is by far not the sharpest pencil in the box, actually quite dumb, I believe she is dumb enough to think her writing that will make her not look like a suspect, I imagine she even got a kick out of it but the whole eternity, exorcism is not something I think Jodie is capable of understanding.