I'll Take What She Has by Samantha Wilde. The book is being released by Bantam on February 26, 2013.
Amazon says this about the book: Nora and Annie have been best friends since kindergarten. Nora, a shy English teacher at a quaint New England boarding school, longs to have a baby. Annie, an outspoken stay-at-home mother of two, longs for one day of peace and quiet (not to mention more money and some free time). Despite their very different lives, nothing can come between them—until Cynthia Cypress arrives on campus.
Cynthia has it all: brains, beauty, impeccable style, and a gorgeous husband (who happens to be Nora’s ex). When Cynthia eagerly befriends Nora, Annie’s oldest friendship is tested. Now, each woman must wrestle the green-eyed demon of envy and, in the process, confront imperfect, mixed-up family histories they don’t want to repeat. Amid the hilarious and harried straits of friendship, marriage, and parenthood, the women may discover that the greenest grass is right beneath their feet.