It is alleged that Manson sent Gillies and other family members to kill her grandmother in order for her to get an early inheritance, but the mission failed when they got flat tire.
During the sentencing phase of the Tate and LaBianca murders, Gillies testified that Manson had nothing to do with the murders. She said the real motivation behind the murders was to get Bobby Beausoleil out of jail by making it appear that the Hinman murders and the Tate and LaBianca murders were racially motivated by a group of black revolutionist. She also said the murders did not upset her and that she had volunteered to go, but was told she was not needed. She also admitted that she would murder in order to get a "brother" out of prison.
On November 5, 1969, Gillies was in a Venice house when Manson follower John Haught "Zero" allegedly killed himself during a game of Russian roulette.
She is said to have never completely denounced Manson and after the Family broke up, she joined a motorcycle gang, married, divorced and had four children.