Hi dancergirl:
I'd start with trying to work out where your DD is at. How would she do if she sat the 11+ today? Not just what the school has told you but how does she do in a test situation.
My eldest is entering Y5 in Sept and several of her friends (who have older siblings so are more clued up) were already talking about the 11+ at the end of Y4. Our State school will not offer advice/ guidance regarding the 11+ - so I bought 'The Parents' Guide to the 11+' from Bond (available amazon & most book shops/ good newsagents). OK they're selling something - but the useful thing is that it explains what the tests involve, helps you to structure your plans about the 11+ in relation to your own child and has some assessment tests to help guide you about how your DC actually is doing.
Going through this process helped me to decide what next and what to focus on - especially areas of weakness.
I think the advice on reading is critical here. Think through what your DD has been reading - if it's been pretty 'low brow' (lots of Horrid Henry, Diary of a wimpy kid, Ben 10, Rainbow Magic Fairies, etc...) but not a lot of children's classics - then use the summer to get her reading from these. This isn't being snobby - the use of language and the more complicated vocabulary really helps here.
A few Classic reading lists here for some ideas:
www.lovereading4kids.co.uk/genre/ess/Bookshelf-Essentials.html
www.guardian.co.uk/books/2000/mar/24/childrens.library
www.commonsensemedia.org/book-lists/summer-reading-list
We're doing longer assessment practice papers, but this is partly because DD1 needs to build up writing strength (the test at our local grammar schools will be 2 sessions of 45 minutes each with a 15-20 minute break between - so I wanted DD1 to build up her writing stamina, which when we started was very bad - as in DD1 close to tears about her hand hurting after 10 minutes writing.
We have a friend who's soon to be Y6 daughter will be sitting the 11+ in September, and she's having her DD work through 10 minute practice papers (one in each English/ Maths/ Verbal Reasoning/ Non-Verbal Reasoning) each day this summer (however there was little or no practice in Y5 or summer before hand). Interestingly, she's taken the attitude that it's up to her DD when, in what order and for how long this DD does her practice. She's bought her a 10 minute egg timer and said 'on your head be it' more or less. The choice locally is very stark - State secondaries typically around 40% (often lower) 5 A-C GCSE versus grammar schools with 97% A - C GCSE or better. She's brought her to the various schools' Open Days - including the state school she'll go to if she does't pass the 11+ - she says that was the single most motivating factor - as her DD strongly does not want to go to the state school having visited the grammar schools and seen the difference in quality, opporutnities and equipment.
HTH