Yes you can if other one has income. But

she has no income. And is not a student. The amount will add back to your income during the tax time. let's say you put $5K and your total income is 105K. In W2 it is 100K with 5K in D. If you are using turbo tax, the 5K will add back. After fill out 2441, it will be take out and still be 100K. But in 2441 line 22 is the smallest of income of two incomes, for her it is 0. In the end, what in the FSA will be added back to their income. Total is still 105K.
So She can have FSA. But do no good for Tax.