Facebook Video violation?

My sfriend was making a video for her husband, and she asked me is there a way to get a song off youtube. I told her to use this converter called Audiothief on Google Chrome. We went through all this commotion trying to edit the video. And she told me when she tried to upload a video it said something about a violation. Can you guys help, are we in trouble? Is there a way to still upload the video? Im worried for her since i told her about the converter... she said she cant upload the video