A case of a female serial killer, active 1985-99, is listed in The Encyclopedia of Serial Killers, under the label “undisclosed” (1948-).” It describes a 14-year span of muti ritual killings.
The Newton listing:
Undisclosed (1948– )
Alleged DATE(S): 1985–99;
VENUE: KwaZulu-Natal, South Africa;
Alleged MO: Children abducted and killed in muti magic rituals; suspect arrested in Sept. 1999 with two children missing since 1996; later led police to several graves; identified as black-magic “healer”
[Michael Newton, The Encyclopedia of Serial Killers (Facts on File Crime Library), Checkmark Books; 2 edition, Feb. 1, 2006.]
EXCERPT: The Human Rights League investigated the muti-murders in  in a study titled the Trafficking Body Parts in Mozambique and South Africa. One of the interview samples included in the report was of a case in Bloemspruit where a woman who wanted to become pregnant went to a “sangoma” (witch doctor) who provided her with a magical belt to wear. Dangling from the belt were children’s fingers and penises.
“She was made to drink a concoction she believed contained human blood and fat and she was given a piece of flesh which she believed to be a human organ, perhaps a heart. She sliced small pieces from the flesh each night and fried them on a stove.”
[“African “muti murders” – organs harvested from live (or dead) victims and sold for good luck and black magic spells,” Altered Dimensions, October 11th, 2013]
The report is online:
Simon Fellows, Trafficking Body Parts in Mozambique and South Africa. Human Rights League, Mozambique, 2008.
For more cases of this type, see: Occult Female Serial Killers