Fashion Star mentor and clotheshorse Nicole Richie wasn't wearing all that much lounging by a hotel pool in Miami's South Beach on Wednesday.

In town for a Tuesday night bash held in honor of her Ocean Drive magazine cover, the 30-year-old mother of two soaked up the sun in a skimpy, dark mauve bikini that showed off her healthy, not-too-skinny bod -- and her recent breast augmentation.

Us Weekly was first to break the news that Richie got breast implants over summer 2011.

"In the past, she said she wanted a lift, though we never thought she was serious," one source said of Richie, who has daughter Harlow, 4, and son Sparrow, 2, with husband Joel Madden. "The pregnancies took a toll," the insider explained of the House of Harlow 1960 designer. "She said breast-feeding killed what boobs she did have!"

Joked Richie via Twitter of her arrival in Miami earlier this week: "Just got to Miami and Will Smith DID NOT pick me up in his ride with the top down. This is bullsh**."