Bro- the universal slang
Dude is a word that has no specific meaning, and the interpretation of this slang has evolved over time. It is typically used to address a male.
The female equivalent is dudette, but it is rarely used. Sometimes, even women call each other dude.
This is the case with bro, too. Even though the female equivalent, sis or sister, is available, bro has made its foothold, and its usage is widespread.