June 09, 2015 09:45 AM

David Livingston/Getty

It’s no surprise Ashlee Simpson‘s baby shower celebrating her impending arrival was a relaxed affair.

The mom-to-be — she’s expecting a daughter with husband Evan Ross, 26 — was surrounded by 65 guests at the party, held Sunday evening at sister Jessica Simpson‘s house.

“It was beautiful weather and her house was the perfect setting … so gorgeous,” says an attendee, who adds that Simpson’s newly-engaged mom Tina helped arrange the event.

“It was very chill and almost like just a get-together than a traditional shower,” adds the guest. “It wasn’t focused on games [and was] more like a big party.”

Simpson, 30 — who “looked gorgeous” dressed in a “super flowy, Bohemian-style” outfit — also shared a little bit of the spotlight with her mom. “Everyone was talking about Tina’s engagement and about her ring. She seems really happy,” says the source.

“It feels new to me,” Simpson told PEOPLE in April about expecting baby number two (she shares son Bronx Mowgli, 6, with ex-husband Pete Wentz). “I’m like, ‘Here we go! We gotta learn how to swaddle again!'”

Can't wait to see you at the baby shower pic.twitter.com/PST1LQIrJJ

— Ms. Ross (@DianaRoss) June 6, 2015

— Melody Chiu

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