Since I don't know how easy Apple stores are to find in Brazil, I'd ask her to get you the white one instead. That way, if she can't work it out you can still try to sell the Air and get the white Macbook yourself. I definitely think you'd get more use out of the white Macbook. If you like the looks of the Air, maybe you can exchange it for the 13 inch Macbook Pro, which is slimmer than the white Macbook (but not as slim as the Air) and has the sleek aluminum looks of the Air. It also has a nicer screen and trackpad than the white Macbook. It's a little more expensive than the white Macbook but MUCH cheaper than the Air.
Personally, I'd never buy an Air. There are too many issues with it for the price. From Wikipedia:
"The MacBook Air has been criticized for having a price premium compared to other notebooks of similar or better specification.[23] The flip-down hatch is a tight fit for some headphone plugs and USB devices, requiring users to purchase either a powered USB hub or an extension cable.
Lacking FireWire, the MacBook Air does not support Target Disk Mode, which would have enabled it to be used as an external hard drive for quick data transfers or operating system repairs.
Several MacBook Air users since the release of the first-generation product have complained of severe overheating causing CPU lockup. The effect can be seen at CPU temperatures as low as 66 degrees Celsius and worsens with higher temperatures...
Some users of the first revision have found that the plastic holding the right hinge cracks under normal use, making the notebook nearly unusable. Additionally, there has recently been a "blanket rule" sent out by Apple to its stores around the world which says that the hinge breaking is caused by "user damage", despite a number of cracked and snapped hinges on the Rev A laptop. Therefore, the expensive replacement of the hinge (ergo, the screen as well) is at the user's expense and is not covered by the warranty."