Which girl is correct in this situation?

Amanda and Sophie plan a trip together. Sophie asks Amanda to front the cost of the trip (plane, car, and hotel). Amanda agrees and fronts the money. A week or so goes back and Sophie backs out of the trip leaving Amanda on the line for $1150 because the whole trip is non refundable. Amanda asks her friend Maddy to go and explains the situation. Maddy agrees and says that she will if work will give her the time off. A month goes by and work has said yes so they put the plane tickets in Maddy's name. Work situations change for Maddy and they're no longer willing to give her the time off. There is still a month left to the trip date. Maddy let's Amanda know the situation and offers $500 to cover some of the expense. Amanda is upset and feels Maddy should cover the whole trip (1150). Maddy counters and suggests that Sophie should pay the remaining $650 as she had originally asked the trip funds be covered for her. Amanda gets upset and says that Maddy needs to cover the full amount or never talk to her again. Amanda also then let's Maddy know that's the plane tickets cost $800 for the 2 people and is non transferable as well as non refundable. Maddy still feels it's fair that she give her $500 as that amount covers her cost of the plane plus a bit extra. What are your opinions? Whose responsible for what?

Which girl is correct in this situation?
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