hiya!
Jolly Phonics is FAB and you are certainly not too late.
Oxford Reading Tree is a scheme based on whole word learning and guessing words from pictures and context - they don't even mind in the early stages if words are read inaccuately; as long as a good story is there. So there are plenty of words that could be read from talking about the pictures and from guessing and the hope is with enough repetition, a few words might be 'learnt' whilst phonics is being taught very slowly and having little to do with reading... - I'm not just slagging it off, by the way - the handbook and info on the web site acknowledges this as the philosophy behind the scheme.
Our language IS a phonetic one; that is, the individual speech sounds in our words (40+ of them) are represented in our writing by our 26 letters alone and in various combinations.
In order to fully master our alphabetic code and begin to work out unknown words for yourself, you need to learn how these sounds and letters work and how to recognise them in words and blend them all together to read the word.
Jolly Phonics teaches this.
By Stage 5, ORT becomes suprisingly decodable, and once children have learnt all the basic spellings for the 40 sounds, and a few alternatives, they can happily start sounding out the Stage 5 stories. In my Reception classes, the able readers, about half the class, could read these books by the summer term and were often at stages 8-10 by halfway through year 1.
Teaching reading through a scheme like ORT is only really delaying the reading process and teaching many damaging strategies along the way. Many kids learn to read seccessfully anyway, despite this, as they have the ability to work out the phonics for themselves with little effort. But it is not like this for all children. Also, the memorising and guessing means lots of children appear to be reading successfully for a long time before their memories fail, the damaging strategies do not support their efforts and they don't have enough phonic knowledge to really work the words out.
Go for it with the JP - there is nothing to lose, and will help make sense of her ORT books, although she may be intrigued about more complex sound/letter combinations in those books than she has learnt so far in JP, as they do use words like 'guitar' (where 'drum' would be great!) and 'chicken' (where 'hen' would be easier for independent reading!)
Good luck, have fun - the minimum you need is the handbook and some Jolly Readers to give her decodable reading material to practise her skills.