Ashlee Simpson Details Relationship with Mother-in-Law Diana Ross (Exclusive)

Ashlee Simpson‘s extended family is overflowing with talent.

After growing up alongside fellow musician sister Jessica Simpson, the “Pieces of Me” singer, 40, married entertainer Evan Ross in 2014 and gained the iconic Diana Ross as a mother-in-law — as well as the rest of the talented Ross family.

Now, Ashlee is returning to the stage with her I Am Me residency at the Venetian Resort’s Voltaire nightclub in Las Vegas through Sept. 27, and she was able to turn to Diana, 81, a legendary showgirl in Sin City and beyond, for advice.

“I mean, Mama D always has the best advice,” she tells PEOPLE in this week’s issue. “I think her best advice is staying true to yourself, staying true to your instincts.”

“She’s got my back no matter what. And her Vegas shows are fabulous,” adds Ashlee of Diana, who’s performed many times in the Nevada city, including at The Venetian.

I Am Me, named after Ashlee’s 2005 second album, the follow-up to her 2004 debut, Autobiography, comes after a long time away from solo music. “I haven’t played a full set in like 20 years, so I’m so excited,” she explains.

The “Shadow” performer adds, “This just felt like the right opportunity to dive back into it and relive this old music.”

During her time away from music, Ashlee and Evan, 37, have been busy raising daughter Jagger, 10, and son Ziggy, 4, as well as her son Bronx, 16, whose father is her ex, Fall Out Boy’s Pete Wentz.

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She’s since found a fan in Jagger, who’s “always listening to ‘L.O.V.E.’ and stuff with her friends.”

Ashlee adds, “The fact that my daughter and her friends are revisiting this music, I’m like, ‘Oh my gosh, what a moment.’ She actually just came to my rehearsal the other day, and she was like, ‘Mom, you sound so good.’ For me, that’s everything.”

The mom of three and Jagger have long connected through music. “She’s definitely influenced me to get up here and go again,” Ashlee says. “We dance together, we get free, we let our bodies go. We do our little modern dances. We sing together. So I’m definitely looking forward to making her proud.”