Four years of a single foreign language in HS (can include middle school equivalent) will fulfill requirements at colleges, meaning none required in college.
Physician here. Spanish is a useful, living language (I took French in HS- before the large numbers of Spanish speakers up north, and German for my chemistry major- back before computers translated everything- how times change).
Latin is NOT at all needed or desired for medicine. You learn the vocabulary as you need to. btw- neither is taking any classes such as an undergrad course in any medical school class- there is a reason you take them in medical school. It seems a waste of time to me when she could be learning more Spanish- and perhaps eventually become proficient enough to converse with Spanish speaking patients.
Your D is best off continuing through the 4th level of Spanish. If a fifth year is offered she should decide if she wants that extra year of culture- by then the fundamentals will have been covered. The four years of the same language would make her competitive for various universities and perhaps free up her college schedule for other courses.
Be sure she takes the most rigorous classes her HS offers (in areas that interest her/required)- it will help her get into colleges and will also best prepare her for college. Once in college she needs to take advantage of the fun electives she would not have time for if she goes to medical school. Her major will be determined by her then current interests- she may choose a totally different direction by then. If she still is interested in medical school she can major in anything she wants- including social sciences and humanities- all she needs to do is take the required courses for medical school admissions (which may have changed by the time she is applying). She needs to get a well rounded education. This includes literature, art (eg art history), music (eg a survey course about symphony), and any other course that piques her interest at the time.