Can I add my spouse as a dependent if she didn't have any kind of income for the whole tax year?

A spouse can Never be claimed as a dependent.  You should be filing as Married Filing Jointly even if one spouse has little or no income.

No. A spouse cannot ever be claimed as a dependent.   File a joint return.  You can file a joint return even if one spouse had little or no income.

When you file a joint return, you and your spouse will get the married filing jointly standard deduction of $27,700 (+$1500 for each spouse 65 or older)  You are eligible for more credits including education credits, earned income credit, child and dependent care credit, and a larger income limit to receive the child tax credit.