Miranda Lambert is "trying to get back to normal"

Although she was reportedly "nervous at first" about throwing herself back into performing, a source said: "She's really trying to get back to normal, and I think being onstage is a part of that."

Meanwhile, the 31-year-old musician's choice to surprise Ashley was no shock to their mutual pals as she has been "leaning on her" during the breakdown of her marriage.

The source told New York Post newspaper's Page Six column: "Ashley is a great friend ... and [Miranda's] been leaning on her.

"She hasn't changed. She kept her own identity within the marriage and maintains her own identity. She wants her privacy."

And the 28-year-old singer/songwriter revealed she loves Miranda "like a sister" so are used to helping each other through the hard times as they've "gone through a lot together".

She told reporters: "I've known her for 10 years, and the love between us truly is like a sister. I knew once she started to hear me sing .?.?. she'd want to sing harmony. That's how we do.

"We've definitely gone through a lot together as friends and through life, but I can see her and I rockin' it out when we're 90 years old, sitting there with a shotgun in our hand, rockin' on the front porch somewhere, like 'The Golden Girls.'"