This is one of those ideas that seems so great- until you get into the details.
First, there is the question of admission to StA’s- not just meeting their testing requirements and medical experience expectations, but also getting a high score on the UKCAT, and getting one of a tiny number of places. The NHS has a hard cap on the number of non-UK/rEU students allowed. The number of international student places for medicine is likely to be lower this year under new Scottish protocols designed to make sure that more places go to Scottish students. In the 2018/19 intake StAs accepted 18 international students from 16 countries, including at least 1 US citizen. In 2017/18 they accepted 14 students from 10 countries, including at least 1 US citizen (note that in both cases there were dual citizens, so the US citizen may also be a citizen of another country, and have applied from that other country- that data isn’t available…
IF she navigates all of that she will have to work on the qualifying to practice in the US as a foreign educated doctor (the AMA has a lot of info on their website about doing that). No surprise: there is a lot of testing and certifying involved.
As for doing a science degree & applying to med school in the US, even with a post-bacc year it is very challenging: many med schools don’t accept international (except Canada) coursework or undergrad degrees. There are ones that do- but you should at least check the rules for your home state med schools.
edit: read your latest post too late, @DramaMama2021! Paging @VickiSoCal, who’s daughter is a Chem student at StAs right now…