Tangerine by Christine Mangan

Think Hitchcock.  Think gothic psychological thriller that happens in 1956.   Alice and Lucy met at Bennington College years before and became inseparable until the mysterious death of Alice's boyfriend.  Alice - always the fragile one - is now married to the slightly obnoxious John whose job has taken them to exotic Tangiers.  Then Lucy appears - uninvited but anxious to renew the friendship.  Then things get really strange - and mysterious.  Getting the drift?  It doesn't take long to figure out who is the most disturbed but even that person is not as disturbing as the ending.