@dozierrrr
The question is going to be, at the time of the sale, did your partner qualify for the exclusion? Would your partner qualify for the exclusion if she filed as a single person this year, or if she filed as married filing separately?
If at the time of the sale, your partner met the residency requirement but was not an owner, then your partner is not entitled to the exclusion, and even though you may be filing jointly this year, your maximum exclusion is $250,000. The fact that you later got married does not retroactively make your partner an owner before the sale. If you co-owned the property and your partner met both the residency requirement and the ownership requirement, then your partner is entitled to a $250,000 exclusion, whether she files separately or jointly with you.
[Updated]
An Intuit employee here says you qualify for the full credit even if you got married after the sale, as long as your spouse met the residency rule (had lived in the home >2 years before the sale).
https://ttlc.intuit.com/community/tax-credits-deductions/discussion/capital-gains-on-home-sale-marri...
