Breakdown:
* Asi es: This phrase means "That's how it is" or "That's right."
* Amiga: This word means "friend" (feminine form).
So, the entire phrase is used to agree with someone you consider a friend.
Here are some other ways to say "That's right, friend" in Spanish:
* Tienes razón, amiga. (You are right, friend.)
* Es verdad, amiga. (It's true, friend.)
* Exacto, amiga. (Exactly, friend.)
* Claro que sí, amiga. (Of course, friend.)