I'm willing to be collaborative and flexible on the details, timeline, etc, but basically she was seeing someone for awhile and her flightiness/selfishness/unwillingness to be flexible, plus his dedication to his own work (whatever that might be!) caused them to part ways. She threw a Scorpio-level hissy fit and absconded to Europe for a bit, where she met her current husband. I always imagined she and her ex had a good bond but it just wasn't meant to be romantic, and they just couldn't fit it into their lives. But, it's possible for them to be good friends and collaborators, if he's at all artistic/musical/whatever.