August 31, 2006 -- CAROLYN KEPCHER, Donald Trump's co-star on "The Apprentice," has heard him say "You're fired!" for the last time - because this time he said it to her, sources told The Post. The icy, 36-year-old blonde - who was running the Trump National Golf Club in Briarcliff in Westchester and helping supervise the Trump National in Bedminster, N.J. - was let go earlier this week. "She became a prima donna," said one insider. "Being on 'The Apprentice' went to her head. She was no longer focused on business. She was giving speeches for $25,000 and doing endorsements."...