The best thing you can do as a parent is look at the past papers yourself, look at what they are asking for each text and then look at the mark scheme and understand the different parts she has to hit to get top grades. I am assuming like most of the country she is sitting AQA, so look at descriptions for Level 6, 5 etc and what comes under AO1, AO2 etc then look at how those apply to say the Macbeth question. This includes language AO2, I am not sure when some posters had children sit their GCSEs but some suggestions on here are a bit off kilter.
There are themes for Macbeth which my children didn't study, Ds2 is now year 12 so this is relatively fresh in my head, but looking at Mr Salles on YouTube (fantastic resource) the main themes are listed as Ambition (hamartia), Masculinity and cruelty, Divine Right of Kings, Tyranny, Fate, Violence, Psychology of Guilt and Reality and Appearance. There will be a quote bank on these themes, either school will have given her one or you can google, there are plenty out there. Some quotes cover more than one theme. Themes should have more than one character referencing the theme.
Essay planning is simply knowing what you will write for each theme or character, a very short list. Also if it is AQA, Salles recommends not "starting with this extract" there is nothing in the mark scheme to suggest you have to do this, it is merely given for the lower ability students to have something to write about rather than sitting there writing nothing. Start with the start of the book, where do we see the theme/character in the question, work through the book with key moments for theme/character, then hit the extract, where does it fall in the book? But as it is given in front of you, you are better off using your knowledge of the rest of the text so only talk a little bit about it. Also the end, how does the end leave you? What does the author/playwrite want? These are made up, fictitious characters and events, it is a manipulation of the reader/watcher. AO3 -context in which it was written, if Lady Macbeth -role of women in society at that time, beliefs in supernatural, stars, etc.
I will be honest, Ds2 hated English Lit, he was very high grades for everything else except English. In November mock he scraped into a 5. He didn't re-read the books they had done them to death in school, this was exam technique, we (and I mean we) looked at mark schemes, past papers, watched Salles, essay planned, flash carded for what happens when ie Act 1 sc 1 brief outline. Especially important for the Shakespeare stuff, but also A Christmas Carol etc what order do things happen in. He got an 8 in the actual GCSE.