"Miranda tried to seem happy, but you could tell she was hurting," an eyewitness backstage at Wednesday night's CMA Awards tells ET. "It was a great night for her because she won an award, but still hard for her."
Lambert accepted the trophy for Female Vocalist of the Year (for the sixth consecutive year, FYI), simply stating: "I needed a bright spot this year." Earlier that night, she performed her heartbreaking new single, "Bathroom Sink," and seemed to be fighting back tears.
But first, Lambert hit the red carpet with a very Stefani-esque pink hairdo. She looked incredible, showing off her figure in a form-fitting black dress by Versace. "When complimented on her dress," a source tells ET, "her stylist said, 'See! It is your revenge dress,' and Miranda responded, 'Absolutely!'"
ET's source also spotted a sweet moment between Lambert and her "Somethin' Bad" duet partner Carrie Underwood backstage at the show. "They hugged and embraced for a long time," the source says. "They spoke quietly to each other with their arms around each other. ... It seemed as if Carrie was comforting her."
Meanwhile, Shelton also performed at the awards ceremony -- which marked the first time that he and Lambert would be at the same public event together since their sudden and shocking split in July. Shelton performed his single, "Gonna," after co-hosts Brad Paisley and Underwood poked a little fun at him.
Underwood said they "couldn't ignore the breakup that really rocked our world. The one that's on everybody's mind. Two people in this very room that we all know and love." Then, the camera cut to Kermit and Miss Piggy.
Shelton didn't seem bothered by the jokes when he stepped out holding Stefani's hand later in the evening. He also tweeted this lighthearted message to Paisley on Thursday, "If there's anybody on earth who's learned to take it, it's me!".