First of all, many pre-meds change their minds. So it would be bad for your daughter to change from a language she wants to a language she’s lukewarm about for med school, only for her to decide freshman year of college she wants to do something else instead.
Second of all, I think Spanish would be more useful for a doctor - doctors can take on more patients if they know another language, and they can also serve underserved areas where Spanish is a dominant language. Memorizing the Latin terminology isn’t that difficult for a reasonably bright person, but learning a new language is a years-long undertaking.