A frail Selena Gomez, troubled by her off-and-on relationship with Justin Bieber and a recent health scare, celebrated her new partnership with adidas NEO Label in Los Angeles yesterday. Sources said an elaborate set had been built for a performance by Selena, who on Monday sought medical treatment for throat problems. A source at the launch told us, “Selena wasn’t feeling up to a performance. She is still having throat problems, so her performance was canceled at the last moment. But she put on a smile, posed for pictures and did everything else she was required to do.” We revealed Selena and Justin split earlier this month when he was flirting with a series of Victoria’s Secret models. But they reconciled and were together at the AMA after-parties Sunday before she visited an LA hospital Monday for a sore throat and suspected bronchitis. Reports said Bieber waited outside in a van during her 20-minute visit. They were later seen dining with friends at Benihana in Encino.