Cinnamon is a female spy who appeared in the DuckTales episode "Spies in Their Eyes", where she hypnotized Donald Duck into stealing a computer link from the Navy's secret sub. After Victor Loser betrayed her, she helped Scrooge McDuck and his nephews prove that Donald was innocent.
Boom! Studios comics
In the 2011 DuckTales comic book by Boom! Studios, Cinnamon, now apparently a criminal again, appears in the "Rightful Owners" arc. She assists John D. Rockerduck to win a bet he made with Scrooge McDuck on who is Duckburg's biggest philanthropist. She hypnotizes Gladstone Gander (who is now named Agent X) so Rockerduck can have his luck on his side and win the bet with it. Gladstone is well known about his unpredictable and unimaginable luck, so John D. Rockerduck is more than sure that he will win the bet, but Cinnamon has other plans, as her powers grow as she says that soon she won't have any need for Rockerduck.
Cinnamon reappears in the DuckTales/Darkwing Duck crossover story "Dangerous Currency", where she is a member of the "League of Eve-il" along with Magica De Spell, Ammonia Pine, and Camille Chameleon. They are in an alliance with The Phantom Blot, the Fearsome Four, and the Beagle Boys. They are also later joined by Negaduck. It should be noted, though, that "Dangerous Currency" was never approved by Disney and is not considered canon (this likely applies to "Rightful Owners" as well).