Its sweet of you to want to help and all, but as with every person who has ever gotten up one morning and realized they were heavier than they wanted to be, you didn't get that way in a week & you aren't going to get the way you want to be in 1 week.
The only "weight" she can change in 1 week is water weight.
Maybe this trip will spur her to start a long-term plan instead of just ignoring it until she gets another opportunity to do something where she becomes conscious of her weight again....
Otherwise she should just enjoy the trip!