She stood trial for treason in 1679 for her alleged part in the "Meal-Tub Plot" against the future King James II,[1] but was eventually freed.
[2] The Jesuit historian John Warner described Cellier as a woman of clear, sharp and lively intelligence but rather poor judgment, a conclusion he reached through her conduct during the Popish Plot.
Among these ladies was the Countess of Powis, whose kindness was shown to, among others, a clever imposter, Thomas Dangerfield, who had a long criminal record.
Becoming aware of this man's lie, Lady Powis ceased to assist him, and in revenge, he decided to denounce her to the government as being involved in a new Popish Plot.
"[2] Dangerfield maintained the story that he had been released from prison through the assistance of Powis and Cellier on the condition that he assassinate the king, Lord Shaftesbury, and others.
[6] The real focus of this prosecution, according to Roger North, was to prevent Cellier from giving evidence in favour of the imprisoned Catholic peers.