She doesn't have to. Hispanics, you keep forgetting Hispanics. Key in battleground states, historically high disapproval ratings for Drumpf. It will not come down to independents. Obama lost independents to Romney. Still won by 4 pts and comfortably in the EC. He lost white women to Romney, 56-42.
http://www.newyorker.com/news/john-cassidy/whats-up-with-white-women-they-voted-for-romney-too
So, let's assume Hillary actually loses white women say 52-48. You'd agree that's probably about as good as Donald will do right? Historic woman's vote for a woman President plus some of the his issues with women will peel away some white women yes?
If so, that would be the best result for a Dem among white women going back quite awhile!
Better than Obama in 12, or 08, or for opponents to Bush.
The reason why women overall preferred Obama in both elections is because minority women overwhelmingly supported him, just like they will Hillary. You know who the highest turnout group is percentagewise? Black women.
Millennials don't have to turn out in monster numbers, Hillary doesn't need to do as well as Obama to win comfortably. She can lose white women, and millennials can come out less, and she will still win, because of the impact of Hispanics in battleground states like FL or CO or NV/NM, or the turnout of AAs in the midwestern states like PA and OH or even NC.