Mature adult love is not about care-taking other people’s feelings. If you did your best to be honest, kind and in integrity while still taking care of your own needs, you have nothing to feel bad about. Not all relationships last; in fact not all relationships are meant to progress. There’s nothing wrong with having enjoyed the time together and then moving on when it’s time to do so. The “relationship elevator” where everything has to be leading up to life-long monogamous commitment is just non-serving to everyone.
I’m sure this woman misses you, but I’ll bet also feels a loss that the narrative didn’t go as she’d been programmed to believe it ought to. The relationship elevator didn’t take her to the top, as she’s been always told that it would and should. But that’s not your failing; it’s the fault of the flawed paradigm.