That does suck. I'm probably in the minority, but imo I don't think 17-23 is that big of a deal. Would I be happy about Bobbie dating a 23 year old? No, not really...but I wouldn't consider him a sexual predator or anything. I'd talk to her about expectations, saying no, and if she decided to go 'all the way' then she'd have to live with that.
I wonder what that woman thought she had to gain by bringing that up so long after the fact? Did she feel better after destroying his career?
The 70's were a different time. My father is 9 years older than my mom, and I have no doubt he genuinely loved her. He still does. She was 15 when they started dating.