It just blows my mind that the grandparents don't get rid of Winnie, or at least put her in the attic when Mo visits.
The Red Winnie might be some sort of Winnie manifesation, perhaps a worse, now unbeatable (to Mo) Winnie since you've succeeded in chasing away the other Winnie.
The reason I say this is because when I was little I had terrible nightmares. I'd have all sorts of nightmares but the kind that I am reminded of here is the one with colors.
They started around 4 when my mom took up on a bowling league. I knew she was leaving and I would freak. I know that sounds funny but the specific details were a tea set and tires. The tea set was pink and was "good". The tires were black and were "bad". The tires always ran over the tea set. To me, bad got good. I have no idea why this was so frightenening or why I chose pink and black or tea sets and tires but perhaps red is a scary color to Mo. Just a thought.
Maybe I read this already but why is he scared of Winnie? Has he said? Does he think she will hurt him? Cast a spell? Hurt you? Just curious.