1. ND has a supplemental major in Arts and Letters Preprofessional Studies. This allows a student to major in something from the College of Arts and Letters (such as anthropology) and then take the additional science classes necessary to apply for graduate work in one of the medical professions (like medical school, physical therapy, nursing, etc.). Molly may have pursued this already. It's definitely possible to do in four years while a student athlete, challenging but possible. Several student athletes do it every year. (Also, at ND, the typical order of chemistry is gen chem, orgo 1, orgo 2, inorganic chem during the first two years. Physics is typically for juniors, and ALPP students generally double up on general biology and chemistry as sophomores.)
2. If you look at Molly's profile on the ND athletics website, it says she plans to major in anthropology and environmental sciences. A major in environmental sciences would have her taking several of the necessary science classes, so if she completed the double major, she might not need to do a supplemental major as well.
3. MCAT scores typically last for 2-3 years (depending on the school), not 1 year. The MCAT was recently changed in how it is formatted and scored, but scores were traditionally good for 3 years. If she plans to pursue a professional career in running, then it might not make sense to take the MCAT now anyways.
4. Molly might not go into medicine if you believe this article below? (Or maybe she does, it's really up to her.)
http://scholastic.nd.edu/issues/66163-molly-seidel-continues-impressive-career-at-notre-dame/