Her learning difficulties were never mentioned on the show nor were they apparent - this came out in later newspaper articles. Although she apparently suffered mild brain damage at birth, it seems to have only affected her academic potential, she came across as a lovely, witty and eloquent woman, although a little socially awkward and occasionally embarrassing in the situation, as are many when they go on stage. I thought she looked perfectly normal for an almost 50 year old who probably doesn't get out much and I assume has little money. She was well dressed and had clearly had made a lot of efffort for the occasion. Perhaps a darker colour would have been better, but apart from that she looked fine to me.
So I don't see it as exploitation - exploitation would have been if she really couldn't sing and the producers had put her through for everyone to laugh at, as is often the case on X Factor. The judges were probably not told of her talent to capture the genuine surprise. The audience was ignorant but she knew what she could do and that she would have the last laugh, her smile before she sang said it all. She clearly has a very supportive family and a very large one at that.
I don't think it was necessarily that no-one expected her to be able to sing at all - many did seem to laugh at her but that could be editing - maybe it was the exceptional talent and performance that took everyone by surprise - and it seems the world by storm. She has well over 2.5 million youtube hits with wonderful comments from all over the world, she has only positive comments on Perez Hilton which must be a first, she is in the American, German and Australian press to probably name only a few. International journalists want to talk to her. A record contract seems certain.
So it seems the few minutes of possible ridicule will have been more than worth it for her, although I am not sure how much was edited in. From what I have read on youtube and other comments, there is a lot of admiration for her now. The vast majority talk only about her voice and how much she moved them. Her appearance is irrelevant - not that I see anything wrong with it, I see people like that every single day, she looks perfectly normal and looks like a very nice person.