What is serendipity?
That's luck... When the chance of something happening is extremely small, and yet it happens to someone. Without luck there is no success in gambling, especially when it comes to slots.
I have had a lot of nice and big wins on slots... but I have never hit a really big win, at least nothing extremely big. I didn't win a life-changing amount. But who knows, one thing is clear: Our chances are small, but if we don't try & try then we have no chance.
Yes, I was thinking what could be serendipity in gambling? So it just boils down on luck, when everything is working perfectly in unison and maybe the God of Gamblers is smiling on you to win that big money.
Maybe you really need that money to pay bills, or in the case of the OP's story, it seems that her life is turning from bad to worse until suddenly she won and that really chance and make a U-turn for the better because of luck.