Another way might be to look at presentation transcripts. Picking two TED talks from the top Google hits for "TED talk transcript", I found http://www.ted.com/talks/christopher_soghoian_government_sur... and http://www.ted.com/talks/susan_cain_the_power_of_introverts/... .
The word "just" appears 4 times from the male speaker, and 12 from the female speaker.
There are 10 from this female speaker, http://www.ted.com/talks/amy_cuddy_your_body_language_shapes... , and 8 from this male speaker http://www.ted.com/talks/tony_robbins_asks_why_we_do_what_we... . Bill Gates uses "just" 8 times in http://blog.ted.com/bill_gates_talk/ while Maryn McKenna uses it 3 times in her talk at http://www.ted.com/talks/maryn_mckenna_what_do_we_do_when_an... .
From this alone we can see there's some variability, as McKenna uses "just" less frequently than any of the male speakers.
Based on this, it's clear that a much larger corpus needs to be used to tell if there's anything meaningful in that observation about the gender preference in the use of "just."
This is excellent science.