Expenses that you take as business expenses against your 1099-Misc income are not generally part of your itemized deductions.  Itemized deductions are things like mortgage interest and property tax, and charitable contributions.   It's true that, if you take a home office expense, you may be including some small part of your itemized deductions as business expenses, but the rest of your business expenses, like purchases and supplies, etc., are not part of your itemized deductions.  So, unless you have real itemized deductions reported on a  Schedule A, your spouse does not have to itemize as well.

If you're still confused about the difference, please add another question here and I'll come back to try and clarify a little better.