Dablazes,
There is nothing in the instructions for form 1040 and Schedule A that says that if one spouse itemizes the other has to as well. I suspect you missed a checkbox under the personal information section. The 1040 instructions state:
Married Filing Separately
If your filing status is married filing separately and your spouse itemizes deductions on his or her return, check the “Spouse itemizes on a separate return or you were a dual-status alien” box.
If your filing status is married filing separately and your spouse was born before January 2, 1957, or was blind at the end of 2021, you can check the appropriate box(es) on the line labeled “Age/Blindness” if your spouse had no income, isn't filing a return, and can't be claimed as a dependent on another person's return.
