On Tuesday, the "Vampire" singer marked the milestone birthday by taking to Instagram to share multiple celebratory snaps — including one showing her posing next to a "spill ur guts" cake.

Sami posted a photo of her pink frosted birthday cake with 21 metallic pink ... she captioned the snapshot. Sami posts photos ...

They then lit the candles and cut the cake. As the night came to an end, everyone took time to say goodbye, snap a few more pictures with the birthday girl and take a cookie version of Teen Vogue ...

Sami posted a photo of her pink frosted birthday cake with 21 metallic pink ... she captioned the snapshot. "Happy 21st birthday to my beautiful Sami girl," Denise wrote in the caption of the ...