Nostalgia for the 90's boom and just coming out of the least partisan and politically charged members of the cabinet. Her numbers will decrease as the election season ramps up.
As for your specific points:
She strongly endorses same-sex marriage.
Fairly generic non-controversial position, almost certainly a majority of Americans support gay marriage
As above.
This is genuinely an unpopular position, but hardly career ending. Obamacare has been pretty botched, but parties have had worse policies and still put up viable candidates.