It's possible, though it is very uncommon.
In the links located below this answer there is an image of one such female who is a fully-patched (and presumably then, a voting member with full rights) female who is a Hells Angel.
This is in Quebec however, which is outside the United States.
It is possible to become part of the group as a female without being fully-patched, however what that would entail would require a discussion with a member of the local Hells Angels chapter in question, as each chapter will have a somewhat different set of standards and culture, even within the same rigid code of honor that they all have in common.
It would certainly be a very uncommon thing to see happen, however.
The cast of Love Child - 1996 includes: Neve Campbell as Deidre Emma Cane as Girl gang Cecilley Carroll as Nancy Helene Clarkson as Marie Catherine Lloyd as Girl gang Adrienne Mannone as Girl gang Stephanie Mannone as Girl gang Jenna Mannone as Girl gang Julian Richings as Tom Sr. Amy Sisam as Girl gang Dov Tiefenbach as Murray Murray Asta Torokvei as Girl gang
I believe it was The Angels
The cast of Dead Friends - 2011 includes: Hanako Cho as Girl Gang Dawson Dunbar as Dead Boy Madison Guppy as Girl Gang Karl Kimmel as Mr. Turtle Clarissa Lee as Topanga Lee Elizabeth Nguyen as Girl Gang Sierra Pitkin as Lola Turtle Gina Vultaggio as Girl Gang
Females are allowed in guys gangs, but I don't think there is an all girls gang.
The cast of A Second Chance - 2009 includes: Ava Allan as Angel Shannon Clissold as Flower Shop Girl Ben Feuer as Judge Arnie Pagan as Gang Leader Daniel Steven DiVito as Charly Porelli
Manhatten
I assure you that they can.
In gang culture, giving a bandana to a girl could suggest a sense of protection or affiliation with the gang. It could also be a way of showing trust or loyalty towards the girl.
Go out with the girl that you have a chance with. It will work better for you.
Whether or not you have a chance with this girl depends wholly on how hard you try, and whether or not she likes you. If she likes you, you may very well have a chance.
Angels By "Within Temptation"
Havoc.