I get the cancelled flights every so often , and two weeks ago I had the same scenario. The change email is very difficult to follow if you are trying to do the changes on a cell phone. I am able to switch the flights forward on both sides with no additional costs, however the seats don't stay the same , so I have to hope for the best that I get the same seats, and I usually do. Did your daughter take a refund or cancel the flight, or half the flight, and then go back and make a new confirmation number?. Doing that will cost you money.