In an update on the long romance, a source told Entertainment Tonight that she is not telling many people about her plans for a wedding.
"She hasn't announced anything because she is being very secretive so only their friends will know and at the very last minute," the source told ET. "This time they are doing everything their own way."
Cyrus and Hemsworth have been together for almost nine years and were engaged to be married at one point. They broke it off in 2013, only to get back together in January 2016. They have since said the engagement is back on.
"The first time they announced their engagement in 2012, they felt such pressure to make it the most spectacular wedding in the world but that was the downfall of their relationship and lead to their break up," the source told ET. "This has been such a long drawn out process that they joke about the idea that when they finally get married people won't believe it's real!"
The source claimed that the couple's careers, plus input from their family, has made it difficult to get married. The Hemsworth family's conservative lifestyle has clashed with Cyrus' rambunctious past, but that is changing.
"Miley had to get through a phase of discovering herself before she was able to commit. And now that she has turned her life around and stopped partying, she is clear minded and knows what she wants," the source told ET. "Liam's mother [Leonie] is finally over the moon to have her as a daughter-in-law."
Elsa Patacky, the wife of Hemsworth's brother Chris Hemsworth, is also reportedly close with Cyrus and has supported her.
There have been rumors of a secret marriage for months, but they all turned out to be incorrect. In October, they were seen wearing rings that appeared to be wedding bands, but ET's source claims these are "promise rings."
"She had been sporting her ring and wanted him to show his love and commitment in the same way," the source explained. "Their friends refer to their rings as 'promise rings' and Liam and Miley are both good with that."
Hemsworth, who is best known for his role as Gale Hawthorne in the Hunger Games movies, has been dating Cyrus since they met during the production of The Last Song in 2009. His next movie, Isn't It Romantic, comes out in February 2019.