Looks to me like you have nothing to work with here. As far as tax law goes, you're still legally married. My impression is that you're not even legally separated either. So your only options are MFJ or MFS.
Under current tax law that went into effect in 2018, alimony paid is not deductible by the payer, and it's not reported as income by the recipient.
If she has already filed her 2021 return as MFS and is not willing to amend to MFJ, then you have no choice but to file MFS and pay the taxes on all of your income, regardless of what you did with that income.
If she agrees to amend from MFS to MFJ (and she doesn't have to) then it's all good. If any additional refund is due, she is legally entitled to half of it. (Half would be figured on the total of any refund received already when she filed MFS, plus any additional refund received after amending to MFJ).
Also, take note that amended returns can take 6 months or more to process. So if any additional refund is due, you'll be waiting quite awhile.
