Taking to Instagram, Miller, 34, posted a snap of herself clutching onto Mullane's back – where she appears to be donning a sparkler on her finger!
"In a hundred lifetimes, In a hundred worlds, In any version of reality, I’d find you & I’d choose you.
Yes today, Yes always. ❤️🐼 #Si @tyson_mullane," Miller sweetly announced that she said yes to his proposal.
Mullane also shared a beautiful snap from the moment he proposed to as he appears to be down on bended knee before Miller – while the two are in a secluded forest. So romantic!
Miller's fellow Home And Away co-stars left a message of congratulations to the happy couple below the post.
"This is such fantastic news to wake up to babe, so ridiculously happy for you. Congratulations 🥂🍾❤️," Ada Nicodemou wrote.
While Georgie Parker commented: "This is incredibly exciting news, and I’m beyond thrilled. Happiness and love to you both 💙🥂❤️"
Miller and Mullane have been together since 2016.
The star was formerly married to AFL star Brad Miller for 10 years. She shares son Lennox, 10, with Brad, and also has a son named Isaiah Loyola, 14, from a previous relationship.