Using readers

Hannah's school seems to have a great early literacy programme. She ahs been doing very well with the first level of books - repeated sentence with approx 1-2 new words on each page eg "we are going to the xxx". Her teacher recently lent me a more difficult reader - Hannah is having some difficulty mastering it - I think the issue is she relies on discrimination to tell what the word is - and this reader is full of rhymes all eventually ending up in the one sentence - so 'rat, mat, sat, cat, fat, bat' are all in there. Does anyone have any ideas on how to help her manage this type of reader? She does fine for the first few pages but once they start using the same sounding words in a single sentence she really starts to struggle.