I’d suggest that you start with the Year 5 Initial Assessments (that are free) in maths, non-verbal Reasoning and English (not the verbal=reasoning one as that has many GL question types in it that are not needed for the CEM Test).Once she has completed these, you will be able to see which topics/question types need more practice e.g. comprehension skills, fractions etc.
For NVR: Try the Revision exercises for each type of question (Revision A is not timed so it is best to start with these), then move on to using the Quick Fire Tests,
For English: Try the comprehensions, but print them first, and also use the Synonym Finders.
For VR: Try the Jumbled Sentences and Cloze Quick Fire exercises (and later on use the CEM style Practice Papers – print only)
For maths: Try the Numeracy Quizzes to start with.
I hope that helps you to get you started. There are lots more tests/exercises that can also be helpfully used for CEM preparation later on during the year.