Hello and thank you for your question. I will be very pleased to assist you. I'm a practicing lawyer in England with over 10 years experience.
I am very sorry to hear of your circumstances. I have ready your comprehensive initial post in detail. I assume what you were encouraged to sign was a deed of guarantee guaranteeing her loan. Have you been shown a copy of what you signed now? Was it witnessed? If so by who?
You mention you had a condition at the time which made it difficult or more for you to remember more than a few paragraphs at a time. In your view would this condition have prevented you effectively from understanding what you signed and would a GP be able to confirm the position?