"How often since then has she wondered what might have happen..." — Michael Cunningham quote meaning

How often since then has she wondered what might have happened if she'd tried to remain with him; if she’d returned Richard's kiss on the corner of Bleeker and McDougal, gone off somewhere (where?) with him, never bought the packet of incense or the alpaca coat with rose-shaped buttons. Couldn’t they have discovered something larger and stranger than what they've got. It is impossible not to imagine that other future, that rejected future, as taking place in Italy or France, among big sunny rooms and gardens; as being full of infidelities and great battles; as a vast and enduring romance laid over friendship so searing and profound it would accompany them to the grave and possibly even beyond. She could, she thinks, have entered another world. She could have had a life as potent and dangerous as literature itself.