Cofelia

"Now they have the children, they won't need the nanny anymore!"

- The Doctor to Miss Foster, before her death.

Cofelia, undercover on Earth as "Miss Foster", was a Matron, an outer space "super nanny", of the Five-Straighten Classabindi Nursery Fleet Intergalactic Class in the early 21st century.

Biography
Matron Cofelia was employed by the Adiposian First Family to breed a new generation after their breeding planet was "lost". (DW: Partners in Crime)


 * Presumably, this happened when the Daleks stole the planet. No information on Cofelia's actual species or planet of origin has, so far, come to light.

Cofelia traveled across the galaxy to find obesity on a great scale, which lead her to Earth. Disguised as a Human, she headed Adipose Industries, which produced a drug that claimed to attract Human fat cells and flush them when in fact it attracted them and galvanized them into an Adipose body. This was illegal because seeding a level 5 planet, such as Earth, is against Galactic Law. Circa 2009, she first activated her drug using the power of the molecules in the human bodies that were supposedly to make the people lose weight.

After the Adipose young were galvanized, they removed themselves from human flesh and waited to be collected by Cofelia. When the Doctor interfered with her plans, she was stopped from killing one million humans in the birth process to create one million Adipose. Instead, they all survived the birth method and the March of the Adipose had only ten thousand young.

A Nursery Ship arrived and beamed the Adipose onboard but the First Family, who knew what they were doing was illegal, decided to rid themselves of their accomplice. After the Adipose were beamed up, the Doctor and Donna attempted to persuade Cofelia to get away when she was in the beam. But when she didn't believe them the beam switched off and she fell to her death. (DW: Partners in Crime)

Alternative timeline
In one timeline, Adipose operations moved to the United States. Whether Cofelia headed operations in this timeline remains unknown, though this probable. In this timeline, the Adipose birth happened successfully at the cost of millions of Human lives. (DW: Turn Left)

Tools
Cofelia possessed a sonic pen which, when capped, resembled an ordinary fountain pen.