A lot depends on how much of a go-getter she is. If she’s willing to aggressively seek out funding and research opportunities, she may do perfectly well at a university. I majored in the sciences at a university and had a terrific experience. (Admittedly, I switched from biology to geology, which had about 1/10 as many majors.) I knew a lot of VERY impressive science majors in undergrad, including one young woman who had published as first or second author in multiple journals, including Nature (!), by graduation and had racked up awards like the Goldwater and Marshall like you wouldn’t believe. Graduate programs were practically fighting to have her, and she wound up doing a PhD and postdoc at Cambridge and Harvard. The diversity and depth of research at universities allows such students to go very far.
If she feels shy about hunting down professors for opportunities or competing with graduate students in the lab, a LAC may well be the perfect option. Likewise, if she feels uncomfortable in classes larger than 30 or 40 students, a LAC may be a terrific option.
In my opinion, it’s best to apply to a range of schools. High schoolers change their minds pretty frequently, so applying to both small and large schools could result in a good selection of options in the spring.