I learned something researching the answer to your question. Indeed, you cannot use your HSA to pay for your spouse’s Medicare Part B premiums if you, the account owner (in this case your wife) is under age 65. But it’s a moot point now that your wife is age 65. So now, you can use money from that HSA account to pay for both of your Part B premiums — but NOT for Medicare Supplement premiums!
There is a short list of allowable expenses. Please read the two articles below:
Read this article as well: https://smartasset.com/retirement/health-savings-account-hsa-rules-for-spouses