Barbra Streisand is reportedly letting the stress of low book sales cause tension in her marriage to James Brolin, RadarOnline.com has learned. Insiders claim the Funny Girl actress is furious because her memoir, My Name is Barbra, only sold a measly 210,000 copies during its first weeks on store shelves. In addition to lackluster sales, insiders claimed Streisand is still reeling from being accused of snubbing late fashion designer Nolan Miller in her book. Stress is now said to be spilling over into the hitmaker’s marriage. In the tell-all, Streisand credits Donna Karen with creating the out…