I know someone who frequented Amandari on her own; she went for the relaxation, the tranquility of the place; being alone wasn't an issue. While Mr. Megatop and I were at Amankila in December 2009, we met a nice young woman from New York, an advertising exec, who was on her own and seemed perfectly content. Some people just want to be on their own sometimes. Amanresorts seem as good a place as any, if not better, for that purpose.
That said, I've only visited amans with Mr. Megatop.