She could enter from land but she cannot come back into the US by plane without a negative Covid test taken within one day or travel.
Air travel to the United States
All air passengers 2 years or older, regardless of vaccination status or citizenship, with a flight departing to the United States from a foreign country at or after 12:01am EST (5:01am GMT) on December 6, 2021, are required show a negative COVID-19 viral test (PCR or Antigen and can be approved at-home/self tests ) result taken no more than ONE day before travel, or documentation of having recovered from COVID-19 in the past 90 days, before they board their flight. Air passengers will also be required to confirm in the form of an attestation that the information they present is true.
