It also marks Aguilera's first time winning as coach.
"I truly believe she is The Voice," Aguilera told the audience.
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Porter, now the mum of two, has detailed on her blog how she knew she needed help.
"I was miserable and overwhelmed with life," she wrote. "I was heartbroken and realising that what had always worked for me in the past was NOT working at all. Not even a little bit."
"I felt trapped, scared, and sad and I was ready to really go for broke or get better. So, I did what every good user does and I prayed to a god I had never believed in and then called my mum."
Porter says she has not "touched a drink or a drug" since October 28 2007.
Adam Wakefield representing coach Blake Shelton finished in second while Hannah Huston of Pharrell Williams's team was third and Laith Al-Saadi of Adame Levine's team was fourth.