Host Ira Glass plays tape of two women who ended up as frenemies.They kept trying to be friends, but couldn't help themselves from fighting. Ira then speaks with psychologist Julianne Holt-Lunstad who has run scientific studies to answer the question: Why don't we simply end these troubling kinds of friendships? Holt-Lunstad's research also shows that these relationships are much more common than you might think. (7 minutes)