When the NC and GCSEs started back 30 years ago, the expectation was that the majority of students would do “double science”. Those taking “single science (a combination of Biology, Chemistry and Physics)” were either low achievers, or those who were extremely high achievers in other parts of the curriculum .I don’t think there was such a thing as separate sciences at that time.
Traditionally, it was typical to do two sciences as part of a “broad and balanced curriculum”. This was the “right” amount of science. I did Physics and Chemistry and six other subjects in the early 80s, so Sciences were 25% of my certificate subjects.
Before the current reforms, it was typical to do two Science GCSEs, and most schools would have students sit one set in Y10 and the other in Y11. With the reformed GCSEs, that option does not exist. It’s either Combined Science (2 GCSEs) or Biology, Chemistry or Physics as separate subjects. The individual sciences have 50% more content over the equivalent strands in Combined Science.
While I firmly believe in Science being 20ish% of the curriculum, I think that extreme talent in the performing and expressive arts are a good justification to alter this balance.
A single science is feasible exam-wise, but it may cause difficulties in your school for timetabling or supervision.
For example, if your DD is just doing Biology, what is she timetabled for when her peers are doing Chemistry and Physics? Is she able to get quality teaching in her main subjects, or is she wallowing in the ICT suite doing “independent study”. Does she get any tuition for the Art and Drama teacher during these slots? Is dropping a science worth it?