I'd go with a CV and a very abbreviated version of why you want to go to med school. Even if you have no real work experience, your CV should list your education, honors, research, volunteer activities, and any relevant experience. Your short "personal statement" should detail what keeps you motivated to pursue med school.
On a side note, I hope this is not one of your primary LORs. You should have at least one person who knows you well enough not to need much prompting to write your LOR. Your CV should only serve as something s/he checks to make sure all the details in the LOR coincide with what you plan to put on your AMCAS. It's fine to have LORs that are formulaic, but one of them should be really genuine and captivating.