autistic teenager who has not washed in over a year

work in a respite for children with disabilities. There is a 14 year old girl with autism who refuses to wash her hands face or even shower. She refuses to change her clothes and can go weeks sleeping and living in the same clothes. refusing to even remove her shoes at bed time.when she is having her period she refuses to remove old sanitary towel which can result in 6 or 7 of them been in her underwear for weeks. some might say that this is neglect which it is and she should be forced to wash and change her clothes. The only problem is she is about 6foot and weighs about 16 stone and when ashed about washing etc she becomes very aggressive assaulting staff and family very badly. she has not always been like this its only in the last year and a half this has happened. she has been forced to have a shower twice and it has taken 5 people to do this and it is morally wrong the way in which it is done. but for medical reasons it had to happen. has anyone any experience in situations like this before..all the professionals involved with this girl have ran out of programs etc and are at there wits ends. has anyone any suggestions or advice
thanks for any help