Yes, your wife should be able to claim MO and should get the tax paid to MD refunded since the Veterans Benefits and Transition Act of 2018 became Public law on December 31, 2018.
But it might take a while for the states to establish their procedures for doing so. Tax preparation software can only be updated after the States establish their procedures. You might have to wait until you can file for a State refund. Keep in mind that her income from MD will be taxable in MO.