That's the story, in the late 6os she started replacing Jamerson on motown recordings. I did a quick hunt and her claims cause a bit of angst in the bassplaying world. Once guy referred to her as the drunk uncle, each christmas her claims get wilder and wilder.
Another guy noted that she was a picker and Jamerson was finger player, so it should be pretty easy to tell them apart.
Never-the-less another reputable article says she has a reasonable claim to be the most recorded bass player of all time (over 55 year session career).