"They sent me very nice letters, but said it was too international for them," she says.
Before she committed to a full-time career as a novelist, Julie worked for thirty years as a writer, producer and director in the media. However, she wasn't making headway as an author and life in Auckland was frantic.
"I had no work-life balance and I decided if I didn't do it now, I never would."
So in 2011 she sold her Auckland house, moved to Cambridge and took the year off to rewrite and self-publish The Keeper of Secrets via Amazon and Smashwords.
After 52,000 copies were sold and five-star reviews started appearing on the internet, Harper Collins New York came knocking.
That space Thomas imagined on the bookshelves of shops all those decades ago was going to become reality.
In her latest novel, Rachel's Legacy, Thomas has expanded the story of the Horowitz family and this time she weaves the true story of the work of the Red Orchestra into the plot.
The Red Orchestra was not a musical orchestra at all but a German spy network working with the allies during World War II. To honour these people, Thomas has used their real names in Rachel's Legacy.
"It's not true that all Germans were complicit with the Nazis. There were about 13 plots to assassinate Hitler during the war, but none of them worked," she says.
"It is the story of how normal Germans were trying to stop Nazi tyranny. They fed them, hid them and smuggled them. Without them so many more Jews would have died."
Thomas will be in three Bay of Plenty bookshops next week to promote Rachel's Legacy and meet the people who read her books.
"It's gratifying to see that people are really enjoying the novels. It is lovely to know that your work moves people as an author. Some of the reviews have been amazing," she says.
"I can die happy now. The harder you work, the luckier you become."
In between times publishing her internationally popular novels, Thomas has moved further south, to Putaruru. She is entrenched in local life and can be found judging the annual short story competition, manning cake stalls and helping children via work with her church.