Whenever Pip kisses Estella’s cheek (and there are two occasions by our calculations), said cheek feels like that of statue. What are statues? They are representations of humans, animals, or events, and they are usually made out of stone or other cold materials. When we hear the word "statue," we think of kings, queens, smoothness, quiet, and rigidity. Estella, though human, tells Pip that she doesn’t have a heart, and in this way, her statue-ness is emphasized. Her statue-y ways are complicated by the presence of two other statues in the novel—the casts in Jaggers’s office.
Jaggers's casts (more bust-like than statue, but you catch our drift) were created on the faces of two men after they had been publicly executed. Their agony and raw, human emotion are captured and preserved in the casts. So one kind of statue indicates the lack of humanness within, and the other indicates the humanness within. In any case, there seems to be a theme of inaccessibility or imprisonment embodied by these statue/bust references. And we know all about prison. Estella’s statue-y way is complicated when, at the very end of the book, we find she has melted into a warm, emotional woman.