I wouldn't worry too much about having close friends at this age. Most of her age peers are probably not quite there with true interactive play, which is likely why she prefers chatting up adults. If she's not bothered by playing by herself, then I wouldn't be bothered either. (I remember being internally quite upset the first time I heard another child say they didn't want to play with my #1 child, until I saw that it didn't bother #1 at all, who just said, "okay," and happily went off to do something else.)
