Although Miley is called "The Laughing Doll", she isn't as friendly as her name seems to hint. Miley is sadistic; enjoys seeing the participants in the death game suffer, and even goes as far to torment them by dangling hope before crushing it. She enjoys toying with their despair as the participants start questioning their chances of survival. Miley also has her own plans and agenda, dropping valuable clues to Sara even as she mocks her. She doesn't care about Sara personally, but she derives amusement in seeing how she and the other participants will react to unexpected information.

Miley's original Japanese name, "ホエミー, Hoemī" is a pun on ほえみ, 'Hoemi' literally means "small smile." VGperson named her Sue Miley in their translation to make up for the pun; as in 'smiley'.

To go more in-depth on her voice:

Miley has a very distinctive ‘queen of darkness’ kind of vibe. She is somewhat similar to Junko (Danganronpa), but Junko is much more wild (and ofc her personality is constantly changing). Miley is cruel to the end (see the end of Ranger’s assessment), I’d probably use the word ‘bloodthirsty’ to describe her, even if she isn’t necessarily violent. Above all, the phrase to keep in mind is 'sickeningly sweet'. That is the most effective description I could possibly give for her character & voice.

You know how in certain shows, especially anime, there will be scenes of the villainess in a dark place, slowly revealed to be doing something atrocious whilst a music box plays over an ominous quivering in the air? That’s her. That’s Miley.

Examples I can think off of the top of my head would be… Medusa/Arachne from Soul Eater, Nui Harime from Kill la Kill, Lust from FMA; and then, actually, I’d say Miley is more similar to Celes (DR) than Junko. The both share the same regal ‘dark’ aura, and Celes’ breakdown in her trial could be compared to Miley’s anger after being hit by Kai. Miley does have more malicious intentions than Celes does, though.