One option might be to take an immersion French course during the summer to leave time for what she wants to do in HS. Take immersion courses two summers in a row then cap it off with summer in France taking a science class or two. I would also get subscriptions to French TV programs and have her get her news and science programs that way. She will be far more fluent at the end of this rather than taking it in HS. And she will have time to read books in French with the slower summer pace.
Other than that, there is no way around the hard math classes and the hard science classes. Best to get them out of the way now. Professors will respect students who faced their fears and took the hardest classes.
I would take some sort of anatomy class at some point in HS even if its human anatomy and a DNA class, even if she has to go to a local college.
As for her major, I would not specialize too soon in Marine Biology. Rather, work on her tool box (ie classes ) and look for a professor she likes whom she can talk her way into working for as an undergrad even if free.
