I think she would tottally move out of her comfort zone when he is around. By this I mean she would talk more, and not just sit in the corner like a doll. Also she would try to act more adult when he is near.
Also I was wondering about how would Rainer react if he ever finds Esther sleeping on his bed, snuggling to his pillow while sleeping? XD
(and sorry for my bad english, I'm trying to make it better XD)