Offseason by Naomi Holoch

Miriam, a translator of French fiction and a former academic, has been in love with her mysterious and apparently heterosexual (as in married to a man) best friend Gabriella for years. When Gabriella moves from New York to Paris, the two friends correspond regularly. Then, suddenly, Gabriella's letters stop and Miriam impulsively boards a plane to France to find out what happened. The characters' long-contained passion erupts and Miriam gets to have the love affair that she thought she wanted. In the course of the involvement, though, she learns some awful truths about herself and the woman she desired.