When spouses file separately, if one spouse itemizes, the other spouse must itemize, even if they don't want to (their standard deduction is--correctly--zero.)
To change this in Turbotax, you must go back to the beginning of the personal interview where you picked the separate filing status , there is a question "will the other spouse itemize?" If the other spouse will not itemize, you can change the answer to No and that will allow the standard deduction. However, if the other spouse does itemize, the return may be rejected from e-filing, and if not, the IRS will send you a bill for back taxes plus interest and penalties, usually about 6 months after you file.
As others have pointed out, this is one of several "costs" associated with filing separately.
