Sly Moore was an aide to Supreme Chancellor Sheev Palpatine. She first appeared in Attack of the Clones and can also be found in Revenge of the Sith.
Moore was from the planet Umbara and was a constant (and silent) presence beside Palpatine. Actress Sandi Finlay portrayed Moore in both films.
Sly Moore appeared in the canon novel Catalyst and several Legends comics and books including Republic 64: Bloodlines (above right).
Here she is from Attack of the Clones #1 (below).