My friend is getting married in Miami
I will not be attending her wedding. I would still like to give a gift, how much
$$$ would be appropriate?

Whatever you can comfortably afford.

Did she register anywhere? Wait to see what has been bought. You have a year to give a gift according to old fashioned etiquette. I'd wait at least until they get back home.

Marriages these days don't get the expenditures on gifts as they did. Too many divorces. I'd say $40 if she's never been married before. And if she has, and you can't go to the wedding... a token present like a small picture frame. Or nothing. That's just me.