My ds3 is 4.9. They haven't finished going through all the letters yet - they usually do one letter sound a day, apart from Friday, but lately they have done less and are consolidating the sounds they have done so far with a few two or three letter words, eg it, go, no, and, etc.
So I would estimate they have done 19/20 letter sounds. Of those, he can probably remember two thirds. He is doing jolly phonics, so he can remember them better if I remind him of the action that goes with each sound.
That said, his strength is unlikely to be English. Like his two brothers, he is exceptionally good at Maths (knew numbers to 100 and beyond before he started school) but I am not sure he is that good at English. I don't know what the other children in the class can do.
He is not reading yet. I am a bit disgusted by this tbh as my other three children were all giiven reading books very early on in their first term. This school though approaches reading very slowly which I suppose is best for many children, but not all.
My advice mummyinred, would be to trust in your dd's seeming intelligence and try not to worry about what she can do compared to others. She is in the younger half of the class and that makes a huge difference at this age. My eldest son is a June baby and it took him until Year 2 before he was in the top groups for English/Maths.