Maybe I'm part of the problem, but in my day-to-day life, I even hear women calling each other "dude" all the time, and it seems like it's become a non-gendered term.
Even the Wikipedia article says this:
By the late 20th to early 21st century, dude had gained the ability to be used in the form of expression, whether that be disappointment, excitement, or loving and it also widened to be able to refer to any general person no matter race, sex, or culture.