Olympia was flooded with messages from friends and fans congratulating her on the exciting news.
"Congratulations to you both," ex Neighbours star Pia Miller commented.
"Wedding Bell(chamber)s are ringing! That was horrible, but I couldn't help myself. Congratulations legends," radio and TV personality Dan Anstey penned.
Comedian Joel Creasey even commented: "Furious it’s not me! Congratulations angel!! xx"
Olympia and Thomas began dating just a month after they first met, which was around the time Olympia's grandfather passed away.
"He has come to me at a good time in my life," she told Who in July.
Olympia revealed that she and Thomas had mainly been isolating just outside of Melbourne in the Daylesford/Hepburn region, where the couple bought their own property at the end of last year.
"It’s been such a mixed bag of emotions if I’m being honest. There are days I have absolutely loved doing nothing, and really just teaching myself to slow down," she said.
"We’ve been doing some work around the house and on the garden, and our chickens are my new pride and joy! I never normally get this much time at home so that has definitely been a blessing."
Essendon player Thomas, however, had to relocate from Melbourne to Queensland and spend time at the AFL hub, but announced his retirement from the sport in September.
Olympia shared a loving tribute to her now-fiancé shortly after the news of his "well deserved" retirement was announced, calling him "the most humble, down to earth and loyal man" she'd ever met.
"I love you more than anything and I can’t wait to see what our next chapter has in store for us. Congratulations on an incredibly successful career my big boy."
Congratulations to the happy couple!