(Like) putty in someone's hands
"Her manner of treating everyone as an adult earned her a loyal following; even the most difficult kids were putty in her hands." ("Watercolours")
(like) putty in someone's hands - very easily influenced or persuaded by someone
She can talk him round – he's putty in her hands. (Macmillan)
"The world was a fantastic, marvelous, awesome place, Rose decided."