She can file under 5 year rule.
There's 4 year and 1 day exception.
Meaning after 4 years and 1 day after she returned from long trip, she could try naturalizing:
"An applicant applying for naturalization under INA 316, which requires 5 years of continuous residence, must then wait at least 4 years and 1 day after returning to the United States (whenever 364 days or less of the absence remains within the statutory period), to have the requisite continuous residence to apply for naturalization.[21] The statutory period preceding the filing of the application is calculated from the date of filing."
Source:
https://www.uscis.gov/policy-manual/volume-12-part-d-chapter-3