A third suspect arrested in the murder of a Rockland County political activist pleaded guilty today at her arraignment.

Andrea Benson was only supposed to be arraigned Thursday, but she instead pleaded guilty to second-degree murder in the death of Peggy Nadell. Benson admitted to shoving and strangling the 80-year-old woman at her Valley Cottage home earlier this year.

Benson also said it was the victim's daughter-in-law, Diana Nadell, who bludgeoned and stabbed the victim in an attempt to obtain a $4 million inheritance.

Benson will now spend 20 years to life in prison. Diana Nadell will be arraigned next week. Two other woman have already pleaded guilty to lesser charges.