Hmmm, there are a few things to consider. How long had it been since she was ridden? Did the saddle fit? Was she sore? Did she act angry and fed up? Or did she just look lazy? And another thing I thought of, when she was previously ridden, was she always ridden away from the other horses? If so, when you saddled her she might of thought that she was moving away from the other horses and didnt want to leave them. If this is right, she wanted to be with a herd. She moves with the pally so she defiantely wants to be in a herd. A horse seeks safety in a herd and by riding her away from the other horses, you are taking away her safety. As you said that she would only walk towards the other horses, this would be my first guess. Its all about understanding the herding instinct. Don't punish her if she walks back towards the other horses as you are telling her to go against her herding instinct. Try to eventually turn her around away from the other horses but ride in the same paddock as them. But then again if it is just plain stubborness, as you said you were a beginner, get an experienced horse person to work with her for a while.
Sorry about my crappy explaining and about the heap of jibberish. But I really hope I have helped :d
Good luck with her