I think you are reading more into that statement than what the quote meant.
Sure there is other people's money. I believe what she was talking about is that you run out of other people's money that you can GET AT. Sure, it accumulates other places. Yet if that is beyond their taxation methods then it is gone as far as the socialism is concerned.
Well I have no idea what she was thinking when she made her statement, but that is my point, the money is always somewhere, other people always have money.
How a government chooses to get that money or if they want to create new money or if we want to live in a society where the few hold the majority of the currency while others cant afford to eat, that is another topic...