Is it that she wants to enhance her college applications by showing that she can achieve a high grade in rigorous college classes that are the equivalent of Calc BC and Physics C? Or is it that she wants a dry run of Calc and Physics before doing them again at college?
Most students who do a PG year are doing it for sports for college recruiting, or to enhance their chances at acceptance to a highly selective college, when their 9-12 record doesn’t seem quite good enough. But it doesn’t sound as if your daughter fits in these categories.
The reason that I ask this is that, aside from highly selective engineering schools, which like to see high performance in such classes in high school, it’s completely normal for engineering students to take Calc and Physics in freshman year, without having had either beforehand. They’re college level classes! So if the issue is that she will be taking precalc in 12th grade, and maybe a physics class that doesn’t require calc in 12th grade, she still would be in good shape to take Calc and Physics in college.
Taking Calc BC and Physics C in a PG year won’t affect ED/EA applications, although good grades in such in the first semester could affect RD applications. Taking these classes at your local 4 yr public college the summer before freshman year would be good prep for taking them again at a highly selective engineering program. If she’s not ready for them in 12th, she’s not ready for them the summer before 12th, either.
My point is that if her goal is improving her shot at, say, MIT, it seems that a PG year with Calc BC and Physics C is a long way to go for that. A lot of kids who take Calc BC and Physics C before 12th grade, and do very well in them, still don’t get into MIT. Summer classes the summer after 12th grade at a nearby state college would be an easier way to get her some possibly gentler exposure, and it would not involve 12 credits - more like 8 at most. She will have already been accepted to college, so it wouldn’t affect her entering as a freshman.
Unless she aspires to a highly selective engineering program/school, her best bet would probably be to simply apply to college, and take Calc and Physics at college, as most people do.