It's mostly him doing it. Dinah's somehow managed to cross into his dream - if this is a dream, and as much as she can wander around and interact, she can't influence it. The door creaking open is solely on Rook. She shares his excitement though.
"Hey - you did it!" She exclaims. "Here, do you want to go first? I can give you a boost if you need to get your legs up."

He still looks sickly and Dinah's doubtful that he can make it on her own. She might be quite petite but she's definitely strong enough to sort herself out.