Article continues below advertisementKimberly Guilfoyle reportedly isn't sold on Donald Trump Jr.'s new engagement.According to a source, Guilfoyle - who previously dated Trump Jr. - has lingering doubts about his relationship with socialite Bettina Anderson, despite maintaining a friendly bond with her ex.Article continues below advertisement"Kimberly knows Don well and they're still great friends, but she has major concerns when it comes to his relationship with Bettina," the insider shared.