I will be in Perú at Christmas if you would like me to hunt your daughter down and give her a stern talking to.

Two ideas.

1) Your ticket is presumably a bit flexible, so changes can be made. If you wanted her to come back in Sept 2012, could you not just call and change the tix and they would re-price it into a fare bucket without the one year restriction?

2) If you absolutely must pay for her to get home in Sept 2012 then cheaper than a one way will be LIM IAD UIO tossing away the return segment to UIO, that will save you about $400.

I'd keep my powder dry if I were you, your daughter sounds flighty and booking it a year ahead will give her ample time to fall in love with an Inca potato farmer, marry him and set up a missionary church.

Keep your eye out for deals, you have a year for a bargain to come along