Thanks for sharing. As for the hard question, there is a Simple answer - money comes from investors or speculators who are buying STEEM from you on exchanges.
But why do they do it? - Because they believe STEEM will cost more in the future, i.e. they believe that the platform is undervalued.
So far, there seems to be more interest in buying than selling, so we have a rapid rise in price. But she should understand that even though the price can and will go both ways, there will always be someone willing to do a trade.
Good luck with the beach house! :)