Willow, 23, was fêted by her mom, sisters and other family and friends Wednesday ahead of her wedding to Ricky Bailey.
Sarah, who is mom to Willow, Bristol, Piper and sons Track and Trig, posted a slideshow of photos on Instagram. She jokingly called herself a "fifth wheel" in the caption.
"#5thWheel! Letting me hang w 'em anyway," the former Alaska governor captioned the post. "And Happy Independence Day!"
Bristol, 27, said on her account that she was having "the best time" at her sister's party. The bash took place Tuesday through Thursday in Scottsdale, Ariz., according to E! News.
"having the best time at my sisters bachelorette party (but reallllllly missing my kids)," she captioned a group photo.
"it's official, i cannot wait!" she said on Instagram at the time. "#MOH #1."
Bristol is parent to 9-year-old son Tripp, 2-year-old daughter Sailor and 13-month-old daughter Atlee. She filed for divorce from Dakota Meyer in January after less than two years of marriage, but later appeared to reconcile with her husband.