While in the case of Hillary Rodham Clinton, it is understandable to refer to her as "Hillary", to distinguish from Bill (though if she is elected President, she will be likely President Clinton, just as now President Bush refers to W.); however, it does seem quite common to the refer to female politicians by their first name, which is undesirable since it implies that female politicians are seen as personal friends rather than leaders.
Which other female politicians are referred to by their first names?
None as prevalent as Hillary, but I've heard this many times, both in real life and on this forum.
Inasmuch as this does happen, it is because we are (with notable exceptions
) civilized people here and it is just plain rude to refer to a lady by her surname sans title, e.g. while it is natural to refer to her as Sen. Clinton (i.e. surname with title), when you drop the title the natural form of address becomes either HRC (full name) or Hillary (given name).