Diego Rivera: Sex is like pissing. People take it much too seriously.
Frida Kahlo: They say never trust a limping dog or the tears of a woman.
Diego Rivera: Thank you.
Frida Kahlo: For what?
Diego Rivera: For making a fat, old, crazy Communist a happy man.
Frida Kahlo: I'm just keeping you honest, panzon.
Frida Kahlo: What do you think matters most for a good marriage?
Guillermo Kahlo: A short memory.
Frida Kahlo: Why did you get married?
Guillermo Kahlo: I can't remember.
Guillermo Kahlo: Who's there?
Frida Kahlo: The ghost of Frida Kahlo.
Guillermo Kahlo: I knew her.
Frida Kahlo: How are you?
Guillermo Kahlo: Lonely. Only you ghosts come to visit these days.
Diego Rivera: Is fidelity that important to you?
Frida Kahlo: Loyalty is important to me. Can you be loyal?
Frida Kahlo: At the end of the day, we can endure much more than we think we can.
David Siqueiros: I'd rather have an intelligent enemy than a stupid friend.
Frida Kahlo: I had two big accidents in my life Diego, the trolley and you... You are by far the worse.
Frida Kahlo: I just want your serious opinion.
Diego Rivera: What do you care about my opinion? If you're a real painter, you'll paint because you can't live without painting. You'll paint till you die.
Frida Kahlo: Did I tell you that I'm going to walk again.
Alex: Yes.
Frida Kahlo: Did you believe it?
Alex: Of course I do.
Frida Kahlo: You'd better, because you are going to miss it.
Diego Rivera: It was just a fuck. I've given more affection in a handshake.
Frida Kahlo: Don't think I am going to sleep with you just because you took me under your wing.
Diego Rivera: Before you came along, I was painting murals and womanizing in peace.
Answer: The Song Frida is singing is one of Diego´s most favourite songs, La Bruja (On the soundtrack performed by Lila Downs). http://www.musicbrother.com/index.php?page=song&id=167156 (german page, but spanish lyrics).