Amy Pickwoad (in-universe)

Amy Pickwoad was an employee of Miss Kizlet whose Twitter was found by Clara Oswald using face-match. Clara used this information to discover where Kizlet's offices were. Pickwoad's account specifically mentioned that she worked at the Shard.

On the orders of the Great Intelligence, Miss Kizlet reset her and all other employees to factory settings, and they returned to their true selves. (TV: The Bells of Saint John)

Behind the scenes
The Twitter profile was based on the episode's art director Amy Pickwoad. (DWMSE 37)