@cfelrod Simple answer: No. You may treat the money as a gift.
But, that is not only because your daughter cannot claim the dependent care credit; it's because she also cannot use her FSA account to pay you with tax free money. Because her spouse did not have earned income, she will have to pay tax on her FSA funds. The additional income will be calculated on form 2441. As such, your Social Security number and amount of income will not be reported to the IRS.
References: https://ttlc.intuit.com/community/tax-credits-deductions/discussion/i-put-5k-in-a-dependent-care-fsa...
https://www.investopedia.com/articles/pf/09/dependent-care-fsa.asp
