Still, it's within a factor of 2. She did beat the market, but it feels like it's within the realm of good decisions / luck, not insider trading.
On the other hand, the article does say it: she copied trading from her colleagues. It's certainly plausible that her colleagues' decisions were that shrewd and gave her a bump.
I wouldn't expect a bunch of lawyers in NYC in 2018 to consistently do much better than average in the market, but in the 60's in 70's the market was completely different. They could probably do much better back then, since information didn't spread as fast, and they were close to it. I mean, at that time I wouldn't be surprised if simply working physically near Wall St. led to better returns.
Though I still think the more remarkable thing here is the amount of time, not the investment strategy. The 31 years of working past retirement age multiplied the total by significant factor no matter how you look at it.