In recent years, she has transitioned into a "commentator" role on news programs, offering opinions on immigration and multiculturalism in Japan—a topic she is uniquely qualified to discuss. Nishida married a non-celebrity Japanese businessman in 2018. The wedding was held in a Catholic church in São Paulo, blending her Brazilian and Japanese heritage. She gave birth to her first child, a daughter, in 2020. She is famously private about her husband's identity, rarely posting his face on social media.

She is also an outspoken advocate for mental health, having revealed she suffered from panic disorder during her 20s due to the pressure of modeling. Karina Nishida broke the mold for hafu (half-Japanese) celebrities. Before her, foreign-looking models were expected to be quiet, mysterious, or simply "eye candy." Nishida proved that a Brazilian-Japanese woman could be the funniest person in the room, the sharpest commentator on the panel, and a successful entrepreneur.

Despite her striking looks, she stood out in the homogeneous modeling industry. However, her unique background—a blend of Latin American warmth and Japanese features—eventually became her greatest asset. Nishida first gained public attention in the early 2000s as an exclusive model for the fashion magazine JJ . During the "gyaru" (gal) era, she was a staple in publications like Cancam and Vivi . Her tall stature, tan skin (a departure from the traditional pale Japanese aesthetic), and confident walk made her a runway favorite for major designers like Kenzo and Issey Miyake.