Certainly there have been female Borg, such as:
But have we even seen a run-of-the-mill Borg drone (i.e. not a character tied to a plot element) who was female?
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Plenty, though you might not have noticed
Here is one of the first drones the Enterprise D crew meets.
In episode Q Who, of TNG. wiki
Note the early Borg design as well.
All of these drones appear in the best of both worlds