the rules say you can use MAGI in the year acquired or in the prior year. if your marital status changes
say from single to married you can use the MAGI and the related filing status limit of the one acquiring the vehicle from the prior year. The prior year MAGI's are not combined.
Proposed § 1.30D– 4(b)(4) provides that if the taxpayer’s filing status changes (for example, from single to head of household) in this two-year period, the taxpayer satisfies the Modified AGI Limitation if the
taxpayer’s modified AGI does not exceed the threshold amount in either taxable year based on the applicable filing status for that taxable year.
https://www.govinfo.gov/content/pkg/FR-2023-04-17/pdf/2023-06822.pdf
pg 10/17 or the one with 23379 in upper right middle column
there is no further guidance as to what the rules are if you jointly title the vehicle.
so yes, you can file jointly for 2023 and use just Her 2022 MAGI
