Troubled pop star Britney Spears is struggling to cope with life in rehab and her family is worried she may drop out of treatment, according to media reports. Spears checked into the Promises Treatment Center in Malibu, California last month after several failed attempts at rehab. And now a source tells Us Weekly, Spears is wavering in her treatment, and her family is worried about her progress. The singer's cousin Alli was on hand to offer support over the weekend, staying overnight at the facility on Friday and dropping by for visits on Saturday and Sunday. The 25-year-old star hasn't left the center since she traveled to a friend's apartment in Culver City, California last Thursday to pick up a bag of new clothes she purchased online from a trendy Los Angeles boutique. The source adds, "(Her family) hope that Britney wills stay at Promises for a month, but they're nervous she might not last that long."