K.C.
My daughter will be 3 next month. She can sing the ABC's and can recite the numbers to 10. But, she can't actually count 10 objects, which is a different skill. She's getting closer, but still skips numbers, double counts, etc. She can recognize the letter "S" (the first letter in her name) but does not know the other 25. : )
Kids learn at different rates and I don't think you need to worry. Flashcards really are not the way to go with such a young child. She needs to learn through play. Make games instead. Play memory style games with the letters - same idea as a flashcard but a lot more fun. Pick a letter every time you read a book and have her find it at least once on every page. Get an alphabet fishing game. There are so many fun, interactive ways to learn at this age. flashcards are not good.
Don't worry. She'll know it soon enough. At least, I hope so, because that's what I'm counting on for my own little girl. :D