On the dating reality series' season 17 finale — which aired on Monday, August 9 — the 30-year-old had a choice to make between Moynes and Justin Glaze, following Greg Grippo's surprise departure. Michael Allio also left the show last week.
During the episode, Thurston admitted that she had considered leaving in light of Grippo's absence, but stayed and went on a date with Moynes.
The pair started their Fantasy Suite date with a paint balloon fight before relaxing with champagne in a hot tub.
Moynes admitted in a confessional that he was nervous about a future with Thurston because of how much she cared for Grippo. "I love her a lot," he admitted. "But if Katie's still hung up on Greg and she can't match that, then there's no point in getting engaged if she's having doubts."
Moynes still bit the bullet and told Thurston how he felt. He said that he fell in love with her on their hometown date when she took off her high heels to play hockey.
"You scored a point and you were backpedaling backwards after you scored it and your hands were in the air and you yelled, 'Go America!' And it was when I remembered that moment, that without thinking about it and without trying to think about it, I just realized. I said to myself like, 'F**k, I love her,'" he said. "I love you and I'm f*****g really excited about life with you."
The brunette beauty told the 30-year-old, "As much as I want to be stubborn and just do like you, it's scary and it's crazy, but I f*****g love you so much and I couldn't be happier that you're here."
After her romantic night with Moynes, Thurston had to tell Glaze how she felt ahead of their scheduled date.
"I was looking forward to today," she told the contestant. "However, I did have my overnight with Blake and in that, I did tell him that I'm falling in love with him. And that is something I can only say to one person. And you are someone I wanted to explore things with, but given how I now feel about Blake, knowing I am in love with him, it wouldn't make sense to have us move forward and go on this date. It wouldn't make sense to have you meet my family and that's where I'm at."
While Glaze was initially stunned, he wished Thurston well. "I just hope you know how special you are and what you bring to the table," Glaze told her. "I hope he knows what he has in you."
After Thurston's aunt Lindsey expressed doubts about Moynes, he seemed hesitant to pop the question, despite getting approval from Thurston's mom. While looking at engagement rings with Tayshia Adams, Moynes told the cameras that he wasn't sure if he could do it.
At the proposal sight, Thurston said that she did not expect to be "falling head over heels in love" with Moynes, but the "night that you said you loved me changed my life forever because I knew in that moment I wanted to love you for the rest of my life."
Moynes told Thurston that he "can't give you what you came here for. Because you deserve a lot more than that. You deserve the world and I'm excited to support you and be there for you every day moving forward." He followed up by asking for her hand in marriage.
After the episode aired, Moynes gushed on Instagram that Thurston was his "rock."