Armgard was the elder of two daughters of John II and Agnes of Bentheim-Steinfurt.

Armgard married on 3 January 1568 Count Eric V of Hoya.

Armgard then married on 26 June 1578 Count Simon VI of Lippe.

Because she had no brothers, Armgard and her sister Walburgis inherited his possessions.

On 27 September 1576, Armgard and Walburgis divided their inheritance: Armgard received Rietberg; Walburgis received the Lordships of Esens, Stedesdorf and Wittmund.