Boys Like Girls' frontman Martin Johnson proposed to Cooke, 30, on Sunday, PEOPLE can confirm. The two have been dating for a year and a half.
The country trio member shared the news to her followers on Tuesday, posting a selfie to Instagram as she showed off her ring.
"By the look of my nails, he surprised me," she captioned the post. Cooke puckered her lips for the selfie while Johnson stuck out his tongue in true rocker fashion.
Cooke — who performs in Runaway June with Jennifer Wayne and Natalie Stovall — received congratulatory messages from her trio mates and other country stars.
Naomi Cooke/Instagram Naomi Cooke and Martin Johnson
"I mean. THE BEST!!!! So so so so excited for y'all!!!" wrote Stovall, 38.
"Eppppicc 🔥🔥🔥," added Wayne, 38.
"OH MY GAHHHHH Congrats!" commented country star Carly Pearce.
Cooke's new fiancé has even worked with Runaway June this year. He co-wrote "Christmas on the Radio" off of their When I Think About Christmas EP, which released in October.
"I'm just so excited. We've had the chance to get really creative with it," Cooke told popculture.com of the EP. "And that's the fun part about Christmas music is that with the classic songs, people already loved them. So we really do get to just put our own spin on something that is already welcomed by a lot of people."
This is their first official project since the departure of Hannah Mulholland earlier this year. Over the summer, the group happily welcomed Stovall to the group.
"There are a number of beautiful, talented, hungry, hard-working young women in town," Cooke told PEOPLE about their new member over the summer, "but finding someone who knows what it's like to be on the road, who knows the difficulty of life on the road, who knows what it's like to work with a crew of guys ... Natalie knows. She's just such a good vibe."