The Lying Game.

Emma, a kind-hearted foster kid who can't catch a break, finds out she has an identical twin sister, Sutton, who - unlike Emma - was adopted by wealthy parents and is seemingly living an ideal life. After their initial meeting, Sutton talks Emma into stepping into her life for a few days while she pursues a lead on their birth mother. Initially excited to do this favor for her sister, Emma soon learns that Sutton has gone missing and could be in trouble. Now, Emma must decide whether to come clean to Sutton's family and risk her own safety in the hope of uncovering her twin sister's true whereabouts, along with the truth about why they were separated in the first place.