" I am the one who is the "primary owner for the HSA from my prior job and always contributed for my wife in there."
To be clear, HSA contributions are individual contributions. The contributions to your HSA are your contributions, not contributions of your wife even though they are based on you having family HDHP coverage that covers your wife and that distributions can be used to pay your wife's or dependent's medical expenses. It's the family contribution limit that is shared between you and your wife who is also by the family HDHP plan, not the contributions themselves.
The HSA is owned by you even though is it was established to receive contributions made through your former employer. Other than the fact that that is were your former employer made deposits of your HSA contributions, it doesn't really have anything to do with your former employer. Any entity can deposit to that account contributions made on your (not your wife's) behalf.
I agree with HACKITOFF and Opus 17. Also, my calculations agree with those provided by HACKITOFF. Since you mentioned contributing $8,100 to your HSA, presumably you yourself are over age 55. As long as your wife signs up for Medicare during the initial enrollment period, which it appears that she will do, her Medicare eligibility will begin on December 1, 2020 and she will be ineligible to make an HSA contribution for December 2020. (The annual limit is prorated for each month). If the HDHP coverage remains family coverage for December, you'll still be able to contribute the full family limit plus your own $1,000 catch-up (totaling $8,100) to your own HSA and your wife could contribute 11/12 of the $1,000 catch-up, $916.67, to her own HSA. If your coverage reverts to self-only coverage on December 1, 2020, your maximum contribution to your HSA would be 11/12 * $7,100 + 1/12 * $3550 + $1,000, a total of $7,804.17 and your wife's maximum contribution would still be $916.67. These calculations assume that all of the family contribution limit is allocated to you and none to your wife.
