Ulta Beauty ULTA.O gained 9.9% to top the S&P 500 index after the retailer forecast strong annual results. By Devik Jain and Anisha Sircar May 27 (Reuters) - The S&P 500 index on Friday was set for its best weekly gain since mid-March as upbeat earnings, strength in consumer spending and signs of inflation peaking eased worries about a sharp slowdown in economic growth. A mixed set of economic data, some optimistic retail earnings forecasts, and less hawkish minutes from the Fed's May meeting brought back investors this week.