I adore Nicky, but I don't want to see him with Rebecca. Just too weird. Also, she is technically "not of sound mind" so I would be surprised if her family let her embark on a relationship with him.
Did they actually say she has dementia? I thought there was one episode where the dr. said her forgetfulness was due to medication dosing and they could adjust it. But then she keeps mentioning her "disease" and how many good years does she have left, and when Miguel went to the cabin with the boys he was worried about Rebecca being alone. I am guessing dementia but did they ever confirm it?