Nail biting situationnnnnnnn!

okay I don't bit my nails.. but my sister does and it is getting to be ridiculous.. shes 19 and shes totally fine with friends and social issues so I don't think its a nervous habit or anything.. but shes gotten to the point where she bites the skin.. and her fingers don't look healty at all. What are ways other than putting like gross tasting things on your nails to help stop biting them. I mean I'm talking hypnotizing and like puncture or whatever it is when they put needles in you haha.. Would that sort of thing work for this nail biting situation??