"I was literally at the end of a road, you know, and coming to a place in my life where I was like, 'Am I going to keep doing this and feeling like I'm not getting anywhere? Or am I going to give this another shot?' And thank God, thank God, I was able to give it another shot," she said.
Chin's coach, Maroon 5 frontman Adam Levine, was also thankful to add a second win to his resume.
"I like to win. This is fun," Levine said after the show.
Javier Colon, mentored by Levine in season one, was crowned the winner in 2011. Fellow coach and country star Blake Shelton then reigned supreme for the next three seasons.
Levine said he had to change his approach in order to break Shelton's streak — a feat he ranked No. 1 on his list of life achievements.
"In the seasons past where I have kind of fallen short in my opinion, if I'm looking at it analytically, it's by not being able to give enough because I've been superbusy," Levine explained. "So I tried to kind of thin things out so I could devote most of my time to just get to know these guys and instill them with the confidence that they needed to win."
Jacquie Lee, 16, from Christina Aguilera's team, came in second while Levine's other contestant, rocker Will Champlin, took third.
Before the winner was announced, Aguilera and Lady Gaga teamed up for Gaga's "Do What U Want" in matching, iridescent outfits.
"This is the first time we've ever met," Aguilera told the crowd after their duet. "I just have to say guys, she's like the most down to earth, real person that I've ever met in this business and female to female, in this industry it's really hard to find that kind of a person."
Celine Dion, Ne-Yo, Paramore, OneRepublic and Aloe Blacc also performed during the two-hour season finale.