Hilary Duff: Me & My Ex Break All the Rules

Hilary Duff doesn't find anything awkward about the Hawaiian vacation she went on with her ex-husband Mike Comrie.

We got Hilary at LAX, and asked about her Maui trip with Mike and their 3-year-old son Luca ... a week after their divorce was finalized. For a lot of people ... it seemed way too civilized, especially for a Hollywood couple.

Check out Hil's answer ... she's writing a new rule book.