Revenge of the Middle-Aged Woman, a novel by Elizabeth Buchan.

According to my journal, I read this is 2006

She HAD it all, a good marriage, a great job, grown children, a home filled with....... But Nathan, can't compete with "long ago" memoris of why Rose married him, so when Nathan tells Rose he "wants out" of their marriage, especially with Rose's young assistant Minty, Rose isn't sure she is hearing this, and when Timon, her boss, informs her the paper no longer requires her services, she is REALLY sure she isn't hearing this!  Rose's life, as she know it, is over or so she thinks.  However, her children force her to put one foot in front of the other, in their own way.  Her former "beau" reappears, but is HE really what SHE wants?  Muddlying along, Nathan and Minty start having problems of their own, but Rose is pretty sure SHE doesn't care, nor does she want Nathan back, as his life begins unraveling, she does know that SHE has become a better person without him.