Due to her political activities, Winnie was regularly detained by the National Party government. She was tortured, subjected to house arrest, kept under surveillance, held in solitary confinement for over a year and even banished to a remote town. She emerged as a leading opponent of apartheid during the later years of her husband's imprisonment (August 1963 - February 1990). For many of those years, she was banished to the town of Brandfort in the Orange Free State and confined to the area, except for when she was allowed to visit her husband at Robben Island. Beginning in 1969, she spent eighteen months in solitary confinement at Pretoria Central Prison. It was at this time that Winnie Mandela became well known in the Western world. She organised local clinics, campaigned actively for equal rights and was promoted by the ANC as a symbol of their struggle against apartheid. In a leaked letter to Jacob Zuma in October 2008, outgoing President of South Africa Thabo Mbeki alluded to the role the ANC had created for her in their anti-apartheid activism: In the context of the global struggle for the release of political prisoners in our country, our movement took a deliberate decision to profile Nelson Mandela as the representative personality of these prisoners, and therefore to use his personal political biography, including the persecution of his then wife, Winnie Mandela, dramatically to present to the world and the South African community the brutality of the apartheid system. Beaten by the apartheid police, she developed an addiction to painkillers and alcohol as a result of a back injury caused by the assault.

Answer this question "Why did she go to prison?" by extracting the answer from the text above.
Due to her political activities, Winnie was regularly detained by the National Party government.