Here’s a possible way to fill in the blanks:

Mike: Is Maria **a** student at your college?
Rosie: No, she's **an** old friend of mine. We were at school together.
Mike: What does she do now?
Rosie: She's **a** computer programmer. She's not English, you know. She comes from **Brazil**, but she's living in **the** U.S.A. at the moment.
Mike: Has she got **a** job there?
Rosie: Yes, she's working for **a** big company there.
Mike: Do you send **emails** to each other?
Rosie: Yes, and I had **a** long email from her yesterday.
Mike: What did she say in **her** email?
Rosie: She said that she was living in **a** nice apartment in **the** centre of **Chicago**.