11 of 14

11 of 14 was a Starfleet officer in the early 25th century. She currently serves as first officer the USS Sally (NCC-201591). 

History
Sarah initially served on the USS Firestorm (NCC-144017-D), eventually being promoted to chief engineer and became first officer of the vessel after the majority of the senior staff had been lost in a battle with the Klingons.

Assimilation and Separation
Prior to 2409, Sarah was tasked to lead an away team to an assimilated Breen Chel Grett warship, but was assimilated and eventually rescued, although complications with the transporter resulted in her being separated into two separate entities; her human, command focused half (still Sarah), and her engineering focused efficiency fueled Borg half, now 11 of 14.

Chief Engineer and eventual First Officer
11 of 14 was assigned as chief engineer of the USS Firestorm (NCC-144017-E), and later the USS Firestorm (NCC-144017-F). When Admiral Nat was replaced by a changeling, she sided with him; eventually leaving and rejoining Starfleet when she discovered his true intentions. She served on a number of vessels and even saw a brief promotion to Rear Admiral, but was soon demoted back down when the real Admiral Nat was rescued. She has since served as first officer on the USS Sally (NCC-201591).

Alternate Universes
11 of 14 has been stated to have a mirror universe counterpart.