Some children are visual learners and some are auditory learners. I read books to my children from when they were very young. We would play games with the books like... ."find the letter A?" or what word on the page begins with "B". I played a lot of word games when we would drive in a car, like "I see something that begins with...."
My son was definitely more of an auditory learner and we would sing a lot of songs or make a beat to a drum, together, to learn colors, shapes, etc..
Sometimes, with my daughter, I would "leave" a word up in the kitchen, taped to the object, like the words, "window" "clock" "yellow" (walls) and sometimes when they would appear in a book, she thought it was cool to read it to me.
If your daughter doesn't like flashcards, find other ways that she can learn. Don't ever try to force her to learn - let her embrace it. You can always come back to flashcards. Just keep making learning fun. You are being very hard on yourself - if you look closely at your daughter, you will see that you are raising a very smart, confident (and stubborn) child. These are very hard things to teach and yet, you have been successful in doing so and that is wonderful! Right now she may be very busy learning so many other valuable lessons that flashcards aren't at the top of her list. I have a son who struggled in speech, however, he had incredible large and fine motor skills, by the time he was 3 years old. Now he is 11 years old and he has an incredible mechanical ability. My daughter loved being read to, as a toddler and young child... however she was a poor reader. Flash to the present.. she is, now, a teen and she is in several honors classes. So... whatever you do, don't look at those "other", so-called advanced preschoolers and judge your daughter against their abilities (and as parents, we do!) There will be those who are advanced but will eventually plateau. Look at the big picture for your daughter. Just keep giving her positive reinforcement and expound on her abilities and keep learning fun!
You are doing a great job!