Unfortunately, currently there isn't much that can be said about the Angelica Fanshawe true story. It could be that she is an individual who has been lost to the annals of history for the general public. If she was a part of a niche community or a family with a long - held secret, the information might be locked away in personal diaries or oral traditions that haven't been widely shared.
As of now, without more context, not much information is readily available. There may be some information if this is a very specific local or family - related story, but we would need to know where to look, like in a particular town's records or a family genealogy.