The bride-to-be showed off her stunning diamond ring on Instagram as she congratulated Chris Pratt on the release of The Lego Movie 2: The Second Part

Katherine Schwarzenegger can’t get enough of her fiancé Chris Pratt — or her engagement ring!

The 29-year-old showed off her diamond engagement ring in a sweet Instagram post she shared on Friday in support of Pratt’s The Lego Movie 2: The Second Part — which debuted in theaters today.

“So incredibly proud of my amazing, talented and hardworking fiancé everyday, but especially today because his movie, THE LEGO MOVIE 2, IS FINALLY OUT!” she wrote in the caption. “These special little characters (that were played with every morning and night) Emmet and Rex are voiced by my love, and he did such a great job!”

She added, “Head to the theater tonight with your friends, family, kids or even with your pup! It’s so much fun and all about the power friendship! Yayyyyy LEGO ! 🥰♥️👏”

katherine schwarzenegger
Credit: Christina Schwarzenegger comment on katherine schwarzenegger instagram post

Her younger sister, Christina, 27, commented on the photo, writing, “You get that [ring emoji] shot hunnay.”

Schwarzenegger’s stunning ring includes an oval center stone, which appears to be set on a very thin simple band.

Jewelry expert Jason Arasheben of Jason Beverly Hills told PEOPLE Schwarzenegger’s ring appears to be a 5-carat diamond, which he says can range anywhere in price from $150,000 to $550,000.

Pratt, 39, announced their engagement on Instagram last month, writing, “Sweet Katherine, so happy you said yes! I’m thrilled to be marrying you. Proud to live boldly in faith with you. Here we go! 💍🙏♥️.”

RELATED VIDEO: Chris Pratt and Katherine Schwarzenegger Are Engaged: ‘Sweet Katherine, So Happy You Said Yes!’

His relationship with Schwarzenegger first heated up 10 months after the actor’s separation, when the couple was spotted out together on Father’s Day having a picnic in the park in Santa Barbara. They were later seen on dates around Los Angeles and outings with Pratt’s six-year-old son Jack in tow.

“They’re both serious about the relationship and hopeful for the future,” a source close to the couple told PEOPLE. “Chris doesn’t just date to date, and neither does Katherine. She’s very excited.”

“Chris and Katherine are very happy together,” added the source. “They’re very compatible and have a lot in common.”

The engagement comes a year and a half after Pratt announced his separation from Anna Faris in August 2017 after almost nine years of marriage.