Nadya Okamoto had the perfect costume for her friend’s Rihanna-themed birthday party: a likeness of the pregnant pop star in black lingerie, based on her iconic outfit at Paris Fashion Week. 

Okamoto was not pregnant but her belly was distended: “I literally had a watermelon-sized bloat,” she said. 

The 26-year-old TikTok creator is vocal about her digestive issues. A video Okamoto posted of the Rihanna costume, showing her “bloated, poo-filled belly,” has amassed 3.8 million…