Fëanor's exile is 12 Years of the Trees, which is about 120 of our years. Fëanor and Nerdanel have been married about 306 years, or 3060 of our years, at this point.
In one version of this story Nerdanel went back to live with her father after becoming estranged from Fëanor; in the other version she "asked leave to abide with Indis, whom she had ever esteemed, though this had been little to the liking of Fëanor". The second makes for a much more interesting story, I think. Though I do wonder whom she had to "ask leave" from? Indis herself? The Valar? Fëanor? Finwë?
The fact that Indis didn't go with Finwë either is implict in the fact that Nerdanel stayed with her, but Tolkien doesn't really go into her reasons - except for a whiny comment much later by Finwë that these days she prefers the company of her son to his own. I extrapolated from there.
Part 170: Things fall apart
Next time: Part 171: Changing the guard
Chibis by tektek.org