Simply going with odds, it's far more likely to be Golden Retriever than Flat Coated Retriever in her heritage ... at least if this dog is in the U.S. There's easily 100 Goldens for every Flat Coat, and that's being generous.
Both Goldens and Flat Coats have very similar breed heritage -- and the golden coat color is recessive so if a golden retriever breeds with a dog with a dark coat, the puppies are likely to exhibit the dark-coated genes. Info Here
Border Collie is a good guess on the other parent. I had a dog that was a Golden & Aussie mix, and looked a LOT like this dog, minus the semi-erect ears (ours had dropped ears).