Stabitha is Mikayla's Machete who she always carries around. Mikayla really cares for her. It was revealed in The One About Mikayla's Friends that Stabitha comes with a matching whip.
When Boomer threw her of a cruise ship. Mikayla tried to rescue her but was forced not to. Instead, she threw a life preserver to make sure she returned home. (Wet Hot Kinkowan Summer)