What was the amount of money in your FSA on 12/31/2016? If the 2.5 month grace period referred to your 2016 FSA plan, then you could have paid her medical expenses from it in early 2017, which would have precluded her HSA eligibility for the first three months.
However, the IRS notes that if the amount in the FSA was zero on the last day of the plan year (12/31/2016), then she gets a pass and all three months are in. See page 4 in IRS Publication 969 (<a rel="nofollow" target="_blank" href="
https://www.irs.gov/pub/irs-pdf/p969.pdf">https://www.irs.gov/pub/irs-pdf/p969.pdf</a>).
So, she has either 11 months or 8 months of eligibility to contribute...
