I took it to mean that there are a decent-sized group of Americans who do believe that (probably not including the OP), and as a result nothing she could have done would have won her those votes.
I don't know how many people voted against Clinton because she's a woman, but I guarantee you it's not 0. As a result, it needs to be talked about. While it'd be a better world if people didn't focus on such irrelevancies, the fact that some do means we can't act like it's non-existant.
Of course, I don't know whether the yea-woman outweighed the nay-woman.
She offered free college education... that doesn't work very well if you quit high school to work in a factory or if you are like me and horrible at math (I can do everything else but that).
Job retraining doesn't work very well because many people train for the same thing. One great NPR story had a person who retrained in HVAC but he said that around 100 other people in the plant trained for the same thing unless if people move they need some sort of manual labor job.
People who worked in a factory are unlikely to start building websites, apps, manage databases, go into business management etc... they need another factory job or a basic income.
I don't think there's any "possibly" involved here.
While I'm no fan of Sanders, I honestly feel like he could have swept the floor with Trump solely based on the fact that he has an impeccable background and seems like a genuinely nice guy. Instead, the DNC shut out Sanders and used dirty tactics to ensure that Clinton got the nomination. That galvanized a non-negligble number of the young people in my social circle against her.