My autistic sister is 21 years old and incontinent, how can I help her?

My sister is severely autistic, MR and obsessive-compulsive. She is non-verbal and has aggressive behaviors.She did great with going to the bathroom and even wiping until her senior year in high school, last year. One day they sent her home because she wet herself, which she hadnt done since she was very little, and then 2 times the next week, until it became an everyday occurance at home and school, and now she wears depends and she doesn't wipe or wash her hands anymore. She seeems to bear down and wet herself when she gets mad but also does it when no one is looking and she seems fine. She is using around 8-12 depends a day, but she still goes in/out of the bathroom every 15-20 minutes. We have taken her to the doctor a few times, but this is extremely hard because she is behavioral and doesn't understand why we are going to the doctor she freaks out in a medical environment and has to be physically taken into the office and shut in the room. They checked for urinary tract infections, blockages and even took blood but they can't tell us what is wrong... so if its not medical and she is just regressing how do you re-teach a grown adult that doesnt speak or have a concept of the words...? We've tried promting her to go to bathroom and tried to use regular underwear so she would feel when she was wet., but she didnt care she went on herself anyway.

[venustiana]

My nephew's autism is also severe, he doesn't talk, signs a little bit and could not get potty trained. He is 23 and he's also diabetic and have celiac disease. About reteaching, have you tried showing her a picture of a bathroom or a person using the toilet?