Mrs McMaster was one of nearly 3000 people who entered the competition and her name was drawn from over 14,000 entries. Readers could enter once per day and she entered the draw six times.
Mrs McMaster "couldn't believe it" when she found out on Wednesday that she had won the trip.
She said she will take her husband with her and they have both wanted to do the train ride through the Australian outback for some time.
"This is awesome, we've always talked about doing it but never did."
The retired couple have never been to Darwin but have visited their son who lives in Alice Springs. "We are looking forward to all of it, it will be an amazing trip."
Mrs McMaster said it will be the first time she has been on a rail adventure, having only travelled the Wairarapa to Wellington train line.
The couple will decide when they wish to take the journey and organise dates through House of Travel.
Mrs McMaster said around August will be best when the weather is cooler.
Normal fares on The Ghan for a gold service twin cabin are $2399 per person.
Mrs McMaster said she is happy she took the opportunity and entered the competition.
"We couldn't be more excited."