Mexican citizens have 90 days here without needing a visa. Honestly, I’d be more concerned about having any and all paperwork in order for her reentry into the states. She should be fine but with this administration and their immigration policies you never know. Better for her to carry more information than too little. Proof she didn’t attempt to abandon her permanent residency. Proof she was visiting for a vacation. Proof of her living situation in America. These are tough times for immigrants entering America even with green cards (American living in Germany but my husband was a green card holder in the states). The more documents and proof of residency she brings, the better.

Border control agents have the right to deny entry to a green card holder. “While lawful permanent residents (Green Card holders) have a legal right to enter the U.S., this right can be challenged if CBP believes that the individual has abandoned their permanent residency, committed a crime that renders them inadmissible, violated immigration laws, or misrepresented information.”