Assuming you have a family HDHP starting on January 1, 2026, she can contribute the full year's amount ($8.750 + $1,000 if over 55 by 12/31/2026), provided there is no disqualifying coverage or change in coverage during the year (example, going from a family plan to a self-only plan).
However, to qualify, there are two deductible amounts that both must be met. Your info isn't clear on this matter.
For 2026, this means:
It has an annual deductible of at least $3,400 for family coverage
It has an out-of-pocket maximum annual deductible, including out-of-pocket medical expenses, that does not exceed $17,000 for family coverage (premiums don't count towards this limit).
For 2026, you would have until the filing deadline for the 1040 to contribute. Generally, the filing deadline is 4/15 of the following year so 4/15/2027
