Rachel Miller, 40, from Nottingham, has paid up to £7,500 to brokers to free girls as young as six.
The girls and young women are Yazidis, members of a distinct and ancient religious community in northern Iraq, who are considered heretics by ISIS.
Around 200,000 Yazidis fled from ISIS in 2014 when they captured the city of Sinjar and many Yazidi females were captured and enslaved.
Mrs. Miller said the first girl she freed had seen her mother raped and murdered and her father decapitated and was herself raped repeatedly for months on end.
Mrs. Miller, who has three children of her own, told the Daily Mirror: 'One girl squeezed my hand, not just a hello...but a squeeze that said a thousand things.
'Touch from those who have been raped and taken into slavery is so significant.
'They shy away from any touch, unless it's from a mother or sibling... to touch a stranger, me, shows that she trusted me.'
This summer Mrs. Miller sold some of her own gold jewelry and took out a bank loan just so she could pay in cash for a 13-year-old girl.
She said she did not tell her husband, who is Kurdish, what she had done until afterwards but she said he is supportive: 'He's proud but he worries for my safety and knows that I sometimes just do things without thinking.'
Rachel has two autistic sons, aged seven and eight, and a 19-year-old daughter.
She also has a network of donors who help with her work.
The United Nations says around 6,000 Yazidi women were abducted by ISIS and they are traded like cattle at markets in Iraq and Syria and even via mobile phone apps.
One sick phone ad read: 'Virgin. Beautiful. 12 years old. Her price is at £9,500 and she'll be sold soon,' Daily Mail reported.
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