Did they forget to poll women voters in NH?
No, they polled them.
But the fact is: Hillary sucks.
I believe the IA numbers (they're probably even too generous towards Clinton), but no way that those NH numbers are true. Barbara Mikulski and Johnny Isakson winning the "hottest Senators ever" award is more likely than Rubio winning NH by 12 points.
Yeah, this looks off - but it only shows Hillary's tremendous weakness among Independents - which NH is full of (50% of GE voters).
Also, we are now having a pattern: Sanders polls much better than Hillary in states where he has a name recognition like Hillary, near 100%.
Hillary would make a winnable race unnecessarily close and turning it into a 2000-like fiasco and trust me, you don't want that to happen again. The US is still too incompetent in handling close elections, even 16 years later. Bernie OTOH would beat the GOP in a landslide ...
You're right that Hillarys problem is independents hate her. Also, Bernie Sanders has the outsider appeal of Donald Trump without the racial, religious, or sex based polarization.