Dude is quite the Cali word. In my nick of the woods (SoCal) it's not uncommon for females to refer to other females as dudes. This has been going on for years. *resists urge to use dude at end of sentence*
An old reddit discussing the topic with the first comment quoted.
Does a guy calling a girl "dude" put her right into his friendzone? : AskMen
the_oogie_boogie_manMale 18 points 2 years ago
"It depends on the guy? I call everyone dude. SO, Mom, friends. Everyone is dude."
Why Guys Call Girls Dude - What It Means When A Guy Calls A Girl Dude Dara Adeeyo is in the greater New York (cultural lag from California) area and this article is from 2012. She writes for Elle, Teen Vogue, Harpers, etc. etc.
"...But does being called "dude" really mean you're just one of the guys? Or is it just a word that's another term of endearment? There are a lot of terms of endearment I'm a fan of; hun, sweetie, baby, girl, and my fave, boo/boo boo. But is dude one of them? Meh...not so much.
Personally, I'm one of those girls who uses dude selectively when talking to girlfriends or guy friends. Dude, it's just a word. But I'm curious as to whyyy guys do this."