I think it's a mix of loose terms (as in just quite what it means to be a 'feminist', a common bugbear around here) and desperation.
I don't know enough about Hilary's (or anyone else in the PUSA race) past policy ideas and support. But we recently had something similar but smaller scale in the UK, with the election of a Labour party leader. There were four candidates. Three of them - one man, two women - were of the professional politician mould. 'On message', focus-grouped, corporate suits trying to ape the right while still holding on to the left base. The fourth - who barely made the nomination but romped home to win - was of the Sanders mould. Old leftist, decades as an MP, stuck by his principles, often to be found giving speeches and shows of support to non-parliamentary campaigns.
There was a move to push the idea that a 'feminist' vote should elect one of the women, in particular Yvette Cooper (who was polling much higher than the other female runner). Cooper has a history of policies and parliamentary votes in Social Security matters which have made life much harder for single mothers - that is, women - but still the idea was pushed by some that her being elected as Labour leader - and possibly then Prime Minister - would be a great feminist victory.
This is feminism in the neo-liberal paradigm (and as such, I think, is barely worthy of the name). It is not concerned with over-concentration and abuse of power, of increased hardship for the many (including millions of women), of corporate and finance interests overriding those of the public, etc. It only seeks to get female hands on some of those levers of power, then business as usual.
And sad as it is, there is a victory in that, within the paradigm.
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Of course, it's probably quite a bit more complicated than that.
You know sometimes, between the dames and the horses, I don't even know why I put my hat on.