My friends MacBook Air is making a strange noise once she opens it, what can she do to fix that?

Can you describe the noise at all?

Should I ask this be moved to the MBA forum for you?

If you are describing a "physical noise", such as a creaking or squeaking hinge, you ought to tender the unit to an Apple Store Genius Bar attendant and have them ascertain the fix. Ther's even a decent chance that the remedy maybe without charge, or a very nominal one.

Make an appointment by following the Support tab on the Apple website.