Jeanne de Châteaumur

She was a noble woman by birth. She was a daughter of the nobleman Maurice IV Montaigu of Belleville. Her first husband Geoffrey de Châteaubriant VIII died. Her second(I forget) she sued and divorced in French court for stealing money form her families estate. Her third this is where it gets fascinating.
Jeanne married Olivier IV de Clisson, a wealthy Breton who held a castle at Clisson, a manor house in Nantes, and lands at Blain. This was about time the Breton War of Succession kicked off and the battle for the ducal crown.
During the Breton War of Succession, the de Clissons sided with the French choice for the vacant Breton ducal crown, Charles de Blois, against the English preference, John de Montfort. The extended de Clisson family was not in full agreement in this matter, and Olivier IV's brother, Amaury de Clisson, embraced the de Montfort party whilst his other brother, Garnier de Clisson, had defended Brest against the de Montforts.
In January 1342, the de Clisson castle of Blain was chosen as headquarters by Robert Bertrand, the French King's Lieutenant sent to aid Charles de Blois.
In 1342, the English, after four attempts, captured the city of Vannes. Jeanne's husband Olivier and Hervé VII de Léon, the military commanders defending this city, were captured. Olivier was the only one released after an exchange for Ralph de Stafford, 1st Earl of Stafford (a prisoner of the French), and a surprisingly low sum was demanded. This led Olivier to be subsequently suspected of not having defended the city to his fullest and to be accused by Charles de Blois of being a traitor to the French crown with no evidence. He would be imprisoned by the crown and after unsuccessful rescue attempts he would be publicly executed. His head to be placed on a pike for all to see and his disembodied body hung from walls.
Legend has it Jeanne took all of her children to see and swear vengeance for the unjust murder. She would sell off her material wealth and raise a fighting force or 400 men to raze French castles. In each one she and her raiding party butchered almost everybody. They left just one or two alive to tell the tale of what they had seen to King Philip. Now fully allied with the Montfort cause, Jeanne continued raiding. The claimant to the Duchy had nominally granted Jeanne lands and the French soldiers there were targetted. Castles at Touffou and Château-Thébaud were annihilated. Soon, the French were in fear of Jeanne de Clissons and they began rallying forces to track her down and put an end to her destructive campaign. However predicting this she and her followers would cross the channel to England. Where she got 3 warships from King Edward III. Painted black with red sails her flagship was called "my vengeance" and her fleet the "Black Fleet" and she hunted French merchant ships killing them no contest. When the English would land forces the 1346 the Black Fleet aided Edward III’s men by acting as supply vessels and guarded the coast against French ships trying to outflank the English via the Sea.