What can someone do if they are denied entry to Thailand despite having a valid tourist visa and all required documents?

I friend of mine has just been denied entry at Suvarnabhumi and is in a complete state. She has a single entry tourist visa from the Embassy in Dublin (Irish passport holder) and it's her second trip this year. First one was on a visa exempt entry. She made one trip last year. She is waiting for the airline to organize her return back home. She had all of the required documents. Funds, return ticket, hotel booking. She wants to know if there is anything she can do? She asked about appealing the decision, but the immigration officer said they would then hold her for about 5 days pending the decision if she chose to go that route.