Same, very confused. Unless there is something to be revealed (which of course it's DPC, so good chance), can't see more than just another notch on the bedhead.
But if she is another 'wham bam, thank you maam', then the clues he is planting seem to be wasted. Perhaps they are not clues and we are reading too much into it. But she's a background girl and not seen anywhere at the Halloween party, that seems weird. Having her and the tall black haired girl side by side in costume photo and the classroom seems intentional. So my gut tells me that she has yet a part to play.
I don't think she'll be a quick fuck, seems a lot of setup and clues for a quickie. So, unfortunately, I suspect she's going to be an unfuckable character involved in someone else's storyline, or a short, easy to resolve story of her own. Or just a random girl that DPC keeps inserting in strange places to fuck with us.
It's all total speculation of course, but I am keen to find out, she's very enticing!