The mother of twin boys found beaten and abandoned at a Del Mar hotel was arrested for investigation of felony child abuse and injuring a child, San Diego County authorities said. Dorothy DeSimone, 25, was taken into custody at Children’s Hospital in San Diego when she came to visit her 2 1/2-year-old sons, sheriff’s investigators said. Officials want to question DeSimone’s boyfriend, Charles Thomas McCoy, 27, of Phoenix, who was seen with the boys at the hotel. ". . . We don’t know anything other than that he’s the boyfriend of the mother,” Detective Mary Stables said. DeSimone was being held at the Las Colinas Women’s Jail in lieu of $250,000 bail. The boys were sexually assaulted, burned with cigarettes and struck hard enough to leave palm prints on their faces, investigators said.