If you are present during the asseessment, try to get the true picture across to the adult needs assessor without causing friction. It is easier said than done, but if you get the chance you need to be honest in a subtle way as your mum will try to give a very different impression. For example, if she claims to be an avid reader but no longer reads, turn the conversation to ask about her favourite author or book. If she claims to be a good cook say how much you have always enjoyed her food, but with an emphasis on the past tense. Whatever she says that is incorrect find a way of countering it so that the assessor gets the point. If this provokes some of the aggression and confrontational attitude that you mention, although unfortunate that too ought to get the point across.