I thought Classics was Latin (for GCSE purposes anyway). Do you mean Classical civilisation?
Equally, what is R&P? Religion and Philosophy?
If she's not keen on working in groups, I'd agree that Drama is probably a bad choice. Though a fair bit of Drama is also literature based, which sound like it would fit in with her interests. My DD is studying GCSE drama, and I would not really have described her as particularly confident either, but she's really enjoying all the analysis work and play devising (ironically performance is probably her least strong part as that's what most children take drama to do!
My understanding of Latin/Classical civilisation history is that Latin is more about learning the language and reading texts in the language whereas classical civilisation is a mix of classical history and classical literature and history is similar to the history bit of classical civilisation but covering more recent time periods!
Latin/classical civilisation/history are sort of similar but different (you could throw English Lit into this pot as well). I'd also say that Religious Studies is similar too (they are all about studying various subjects and then showing your understand the facts and can form our own opinions by making considered reasoned arguments about them - Latin is less similar in this respect). Assuming she is taking maths and science as well, it would be as balanced a set of choices as most students focusing on humanities are.
I do agree she's potentially picking a lot of writing heavy, very academic subjects and it would be good to pick one that offers some light relief (though Drama contains plenty of writing too!).
(For info, my DD is taking Englishx2, maths, science x2, Spanish, art, drama, history, religious studies. She finds it fine :) I think she'd find it a lot more onerous if the art was something essay based instead though.)