My daughter did A-Level English Lit and is hoping to begin a degree in it in the Autumn. For context, her course consisted of:
Pre-1800 Literature: 'Hamlet', 'The Duchess of Malfi', 'The Merchant's Prologue and Tale'
Comparative and Contextual study - American Literature: 'The Great Gatsby', 'The Grapes of Wrath', Unseen American Lit passages 1880-1940
Coursework: T.S.Eliot's poetry (1,500 words), an extended essay comparing 'Translations' to 'Atonement' (3,000 words).
She found the most useful wider reading she did was reading critical interpretations of her set texts by academics and reviews of different stage productions of the drama texts. For some questions, the mark scheme rewards you for engaging with critical ideas, but she also found that reading criticism gave her inspiration and helped her adapt to the standard of essay-writing expected at A-Level. She found the criticism on websites like JSTOR and the British Library and also used Google Scholar as a search engine to locate articles.
Additionally, for some texts marks are awarded for discussing context (for my daughter's syllabus, this was for the essay question where she compared 'The Duchess of Malfi' to 'The Merchant's Tale', all American Lit essays and her extended piece of coursework). For these texts, part of her wider reading aimed to understand the time period in which they were written better. For example, for 'The Merchant's Tale' she read 'A Time Traveller's Guide to Medieval England' and for unseen American Lit, she read numerous non-fiction and literary non-fiction texts about the Jazz Age, the Dust Bowl, civil rights, feminism etc.
All of this secondary reading isn't useful without an understanding of the primary, set texts. The best thing for your daughter to do would be to email the Head of English at the school that she's planning to go to for Sixth Form to find out what the set texts are. If she reads the set texts over the summer holidays and gets a sense of the plot and characters, when she comes to study them she'll be in a better position to dive straight into analysis and secondary reading which facilitates thinking critically about the texts, rather than having to first grasp what is going on in each book.
The most important thing to identify is if your daughter's course has a