In US English slang, the word "man" is more often used as an interjection not necessarily to address the particular speaker. It's not necessarily an ethnic usage of the word. It is an interjection with both "This is dope, man", and "Come on, man." So yes it is okay and reasonably common to say "Hey man" to a woman, although it is probably more common to use when talking to a male friend. For example, "Hey man, I was just kidding.." could be said to either a man or a woman. (And you would never say "hey woman" to someone.) "Oh man", also is another common expression - meant to express disappointment or annoyance. "Oh man, we have to clean up this huge mess by ourselves." You could say this to either a man or a woman as well.

Generally they would drop this style. I suppose you could say “what’s up man?” to a woman, but the woman might find it a bit odd. Some women however may say “what’s up man?” to you, and this is normal.

Yes, my sister and I both say "man" to each other. 😆 We even say it to our mom sometimes. And as Tracy says, this usage of "man" isn't really connected to any particular race, ethnicity, or region of the US. It's just an informal usage of the word. ("Ma'am," on the other hand, would be very formal.)

I want to add that "dude" is also really common slang all over the US (especially on the west coast where I live). I always call my female friends and coworkers "dude" without any problems: "dude, did you just see that?" There is a female version for the word, "dudette", but nobody says it. Like, that's just weird, dude.

Can we practice English together?