Faithfull and Jagger dated from 1966 to 1970, and their relationship was known — then and now — to be nothing short of stormy, or at the very least, never boring. In 1967, during a drug bust at Rolling Stones' member Keith Richards' Sussex home, Faithfull was found by the cops wearing nothing but a fur rug (via New York Times). Richards and Jagger were put on trial, but Faithfull made headlines like "Naked Girl at Stones Party” as well.
"I was slandered as the wanton woman in the fur rug," Faithfull wrote (via New York Times), "while Mick was the noble rock star on trial."
The pair were also known to have been, well, not entirely faithful to each other (via AzCentral). During that time, Jagger famously had an affair with Marsha Hunt, with whom he'd go on to have his oldest daughter, Karis. Jagger also cheated on Faithfull with her best friend, Anita Pallenberg, while the two shot the 1970 film "Performance" (via Ultimate Classic Rock). Pallenberg at the time was dating Richards, and had been involved with Rolling Stones member Brian Jones as well, before his death in 1969 (via Rolling Stone).
So what choice did Faithfull have, except to sleep with Richards?