Monnie was inside Wentworth for bashing her "weasel of a husband" Fred Ferguson.
Upon her arrival at Wentworth, Vera Bennett intoduced Monnie to Bea Smith, hoping to cause some friction, but it turns out Monnie and Bea were old cellmates, and happened to get along very well to Vera's dismay, despite the fact the two often argued.
Not long after her arrival, Monnie is framed for drug smuggling by Barbara Davidson, and we don't see her again until Ep 029, when ex-screw Anne Yates is an inmate at Wentworth. After Anne stabs Bea, it is Monnie who raises the alarm.
Monnie agrees to help Joyce Martin by moving the proceeds of a payroll job when she is released, in return for a cut of the profits. Monnie does this to help her husband Fred pay off his gambling debts, but Monnie ends up bashing the living daylights out of him when she finds out he overestimated his debt in order to gamble the rest. Monnie is sent back to Wentworth when Fred lays a charge.
Upon the arrival of new prisoner, child murderer Bella Allbrecht, Monnie is the first person to attack her in the garden. She later becomes the main suspect when Bella is found dead, although Monnie is cleared when Martha Eaves is tricked into confessing.
Monnie refuses to bow down to new prisoner and Top Dog Toni McNally, and as a result Monnie is accused of being a lagger when Toni's stash is found, however Monnie actually fed Vera false information.
- Although they share a surname, Monica is no relation to Joan Ferguson.