Looking for advice on booking the following Christmas holiday itinerary for my daughter who is in college in Fayetteville AR. Basically we want her to spend two weeks with us in Portland OR from Dec 14 to about Dec 28. Then fly her to Santiago Chile to visit her grandparents over the New Years, returning back to Fayetteville on or about Dec 11.

What we want to do is the following:

Dec 14: XNA - PDX
Dec 28: PDX - SCL
Jan 11: SCL - XNA

Makes the most sense to route the flights through DFW because they have direct flights to all three destinations. I went to the AA web site and when I entered this entire itinerary as a multi-city flight the cost comes up to over $8000.

Alternatively if I book the domestic and international segments separately I get it down to about $2100 as follows:

Domestic multi-city portion: $683
Dec 14: XNA - PDX (via Chicago)
Dec 28: PXD - DFW
Jan 12: DFW - XNA

International portion: $1532
Dec 28: DFW - SCL
Jan 11/12: SCL - DFW

So questions: Are there any pitfalls to buying two separate tickets as shown above, all on American? Can I then link the itineraries so that if one flight is cancelled or delayed they will re-book any other necessary flights free of charge? Mainly the issue is making the international connections in DFW. We can make sure that she gets into DFW with plenty of time to spare for the connection to her Int'l flight to Santiago. But if there is still some problem with the connection will American re-book her on a different flight to Santiago without cost? Same thing on the return, if she misses her continuing flight to Fayetteville will they accommodate her?

Any other general advice for putting together this kind of itinerary on American?