The 23-year-old actress reunited with Ukrainian heavyweight boxer Wladimir Klitschko, 37, in January, two years after their split.
It's now been claimed the pair are preparing to make their romance official and have started planning their wedding.
"Very few people know, and she isn't wearing her ring publicly yet," an insider told Us Weekly.
Hayden dated American football star Scotty McKnight following her break-up from Wladimir, but they went their separate ways towards the end of 2012.
It was soon speculated that she and the boxer were giving things another shot, with Hayden spotted visiting him at his home in Florida. Although she insisted they were just good friends in January, during an interview earlier this month Hayden admitted they are back together.
It's suggested they are wasting no time in planning their nuptials.
"Looks like a summer wedding!" the source added.
When admitting she is dating Wladimir again, the actress spoke of how odd she finds the interest in her personal life. It's something she doubts she will ever get used to.
"People think it seems very strange from the outside, then they see the inner workings of it, and they understand it," she told British newspaper The Telegraph. "But I didn’t become an actor to put it out there for the world to judge. The fact is, I’m happy, and that’s all that matters."
The blonde star also spoke of her desire to have a family before too long, claiming she was "built" to be a mother and it is one of her main life goals