Poor research seems the likely culprit but misinformation like this spreads online, especially from 'trusted' sources like the Guardian.
The evidence certainly points that way especially when you consider how quickly she was discarded by Donald Cammell with whom she had been in a ménage à trois, along with Cammell's then girlfriend Deborah Dixon, since 1967 , shortly after filming had finished.
Such was the first screening for Hollywood executives of the British film Performance, starring Mick Jagger, Rolling Stones muse and super-groupie Anita Pallenberg, and Michele Breton, an androgynous 17-year-old French 'actress' who'd been spotted on a beach by the director.
Joan Chen and Anne Heche in Wild Side Cammell completed just three films in the next 25 years, Demon Seed with Julie Christie in 1975, White of the Eye in 1987 and Wild Side in 1995.
Michèle Breton is an actress, known for Performance 1970 and Odissea 1968.
Michèle's name even comes up in the auto suggestions list, yet a vast amount of the information relates purely to her role as Lucy in the cult 1968 British film.