Natali Germanotta doesn’t share the same outlandish fashion sensibility as her older sister, Lady Gaga. Natali, 18, who had a cameo in Gaga’s new “Telephone” video and has reportedly been taking vocal lessons in hopes of joining her sib as a backup singer, showed up to her own birthday dinner at Sazon in TriBeCa in an understated, elegant black frock. “She dresses and acts nothing like Lady Gaga,” a spy said. “Everyone stuck to soda because they were all under 21. They were all very polite.”