Keep saying "NO" firmly whenever she barks. When she stops barking for a moment immediately love her up and let her know that this is the type of behaviour that pleases you. If she begins barking while you are praising her, immediately stop praising her and give her the command "NO" again. When she stops barking again, begin praising her again. If you get to her everytime she starts barking; and, remain consistent, eventually she will equate the word "NO" with stopping barking.