Indeed. That question came to my mind as well. They clearly don't have a sour relationship, and their relationship wasn't ended because of familial issues, nor incompatible orientations, so my best guess as to why is that they simply went onto different paths in life.
For instance, one (frighteningly-realistic) possibility is that when Rain's mother Lilith died, Fara didn't have the ability to maintain her relationship AND look after Rain. Especially given who Rain wanted to become.
I think it was more them drifting apart than an acrimonious break up. Which raises a tantalizing possibility - would Fara rekindle her relationship with Vincent given the chance? How would it affect his work with Rain?
Because it would affect the relationship between Rain and Vincent, and because she would do just about anything for Rain, I doubt she would ever rekindle her relationship with Vincent while Rain is still seeing him. For that matter, Vincent seems to professional to date someone so close to two of his clients.
For instance, one (frighteningly-realistic) possibility is that when Rain's mother Lilith died, Fara didn't have the ability to maintain her relationship AND look after Rain. Especially given who Rain wanted to become.
Butyeah, looking forward to getting the answer.
http://rain.thecomicseries.com/comics/304