It is never too late. However, there will be the many chemistry and other science classes to fit into a schedule. There was a reason this student chose to avoid science courses in college. A change in perspective now. Classes for the major (easier to keep it than to change to a STEM one) plus the many hours for chemistry labs et al will mean some heavy academics. But- easier while still in college and good prep for the rigors of medical school. If a semester filled with science is not liked the answer to becoming a physician will become more clear.
Go for it. Discuss course tactics with a faculty member involved in the premedical intention. There is no fixed “track”. Many ways to get required classes and still major in a nonscience. The “worst case” scenario is to alter one’s schedule to fit in many otherwise unneeded science courses and discover the goal is not worth the path to get there. However, even this scenario will teach the student something- there is a (good) reason to not have taken college sciences before. Better than not trying and always wondering if one should have. A lot easier to use a semester or two as an undergrad than to sign up for post BS/BA classes at a huge expense only to discover a lack of interest in those needed basic sciences.
“Nothing ventured, nothing gained”.