Firstly, it’s great that she has good social skills and independent dressing, toileting etc. Those things are the most important really, which should mean your DD will settle well at school and be a pleasure to have in the classroom.
I agree with AladdinMum that it’d be worth getting her vision checked if you haven’t done so recently, and also that learning should be through play at this stage.
For learning the alphabet and numbers, how about some really nice puzzles? My DD had a very long alphabet train puzzle which had each letter in upper and lower case. We had lots of fun finding the next letter (remember to use phonic sounds though, not ay bee cee etc).
Alphablocks on the TV is also brilliant for learning letters and sounds.
You can also play spot the letter when you’re out and about – maybe start with seeing if she can spot the first letter of her name on any car reg plates in a car park etc? Also in books, of course, when you read to her (which I would suggest you do every day, if you don't do so already).
You can also work on aural recognition of letter sounds, so get her to say the sound for the start of ‘cat’, for example.
For counting, always count the steps as you go upstairs, and count out the sausages when preparing dinner etc. See if she can put a cup on the table for each of you at mealtimes, and count them as she goes.
Basically, at this stage I’d just incorporate this sort of learning gently into everyday life, but try not to worry, because she sounds like she’ll be fine at school.