Ms. Ross chimed in: “Sex can be playful, more like, ‘Let’s have some fun.’”

Ms. Dodson’s epiphany arrived in the wake of a rocky, sexually tepid marriage in the early 1960s to an advertising executive, Frederick Stern. The couple had no children, nor did Ms. Dodson, who grew up with three siblings, plan on having them in the future. “I watched what my mother went through,” she said. “It’s the most thankless job on the planet.”

Free to experiment, she explored group sex with women and men, her objective, she said in a 1970 New York Times interview, to let go of jealousy and possessive feelings, “to understand I could love more than one person.”

She eventually became disenchanted. “Organized group sex is a little bowling-league kind of thing,” she said at the time. “It’s super‐compulsive — there’s a frantic quality to it. It’s weird.”

With a small settlement from her divorce, she financed the first of the sex workshops for women that were to become her livelihood and calling. At them, she urged often skittish participants to strip down, discover their bodies and embrace practices involving clitoral massage and the use of the Magic Wand, the slightly unwieldy but highly efficient vibrator she promotes and sells through her website, Dodson and Ross.

Her closely shorn white hair and sagelike demeanor invites comparisons with Dr. Ruth Westheimer, the cozily entertaining sex guru who mainstreamed in the 1980s. Ms. Dodson isn’t having it. “Dr. Ruth is your grandmother with a funny accent,” she likes to say. “You never listen to what she says.”

The comparison is apt — to a point, Ms. Sprinkle said. “Dr. Ruth is safe, whereas Betty is edgy, a progressive explorer of sexuality. She has the kinds of experiences that even her younger followers will never have.”