Hillary won’t owe SS anything. Advance on royalties is paid regardless of whether or not the book sells. She won’t get any royalties on the book because it won’t earn back the advance but the $14 million will be hers. She’s probably already received half of it, although ti can vary how the installments of the advance are paid.
In all the hoopla about this book, I don’t recall anything about ‘royalties’. What I’ve heard “paid”, “got”, “advanced.”
Additionally, I find it difficult to believe a reputable book publisher would pay an irrevocable ‘advance’ without some stipulation that sales must be commensurate. It goes against all business sense.