Start at the beginning, and get an idea of what she can and can't do, and then you can see what you need to work on.
Does she know number bonds to 10?
Number bonds to 20?
Can she reliably add and subtract within those ranges?
Number bonds should be instant recall, if she has to stop and think about them then you need to practice those until they're automatic.
Does she understand that subtraction is the inverse of addition (eg that if 6+4=10 then 10-6=4, etc)?
If she's confident with easy addition and subtraction, does she understand place value, and adding and subtracting in batches of 10, eg. 56-10=46 etc etc.
Once you're secure with that, then move on to multiplication:
Does she know her 2x and 10x tables? She needs to LEARN those until she can recall any of them randomly, ie. out of sequence rather than needing to recite the whole 2x table to work out what 2x9 is.
Then she needs to understand that multiplication is commutative, ie. if 2x9=18, then 9x2=18.
Point out the connections between 2 x table and doubling/halving.
Make sure she understands that division is the inverse of multiplication, ie that if 2x9=18 then 18divided by 2 is 9. For some reason the NC doesn't plug that as much as it should, and it's an important point.
Once you've done that, do 10x table (which they mostly find easy) and 5x (bit harder). Again you need instant recall, and understanding of equivalents and the connection with division.
Don't panic, I discovered massive gaps in my Y2 child's maths at the beginning of the year, but have been working steadily on it since then and she's pretty much caught up.
If you find specific weaknesses, there are good worksheet generators on the internet (google 'primary maths worksheets', or 'times tables worksheets' etc). Woodlands Junior School have online maths games. You can also buy workbooks to teach at home -- some are better than others, some can be a bit gimmicky. Bond do one called "No Nonsense Maths" which is pretty gimmick-free, and Andrew Brodie do one called "mental maths every day" which is ditto.