I've had similar experiences, although not over such a long timeline as that. And you followed my number one rule for success in the bowl: Never be an asshole.
Never, ever, no matter how extreme the provocation. No matter how bad the flakiness. No matter how bat shit fucking crazy they are.
Be a gentleman. Be a gentleman even in the face of stupidity, inconsistency, flightiness, indecisiveness, craziness, rudeness.
NOTHING will set you apart from so many SDs other than Just. Not. Being. An. Asshole.
Why did this sweet little SB approach you after so long? You were polite! You weren't a dick when she made it clear that she wasn't (yet, as it turned out) ready to have sex. So, when she needed money, who did she think of? You. Of course.
“Being male is a matter of birth. Being a man is a matter of age. But being a gentleman is a matter of choice.”
― Vin Diesel
Who knew ole Vin was such a philosopher? But, I promise: It will also get you laid pretty regularly. And, apart from that, you get to feel good about not being an asshole!