Learning should be fun. If now, at the age of 5 learning is a 'chore' it will always be a chore to her. When I was 15 months old I was apparently able to speak 2 and 3 word sentences. My mother lost me in a store because she let me wander around a jewelry counter alone because I wanted to see my Aunt on the other side. It freaked her out so badly, she FORCED me to memorize my mothers entire name, my fathers entire name, my address, my phone number and the phone number of where my parents worked. At 15 months! She would force me to recite it for friends, family, and strangers. When I didn't, I would get a spanking.
I always loved to learn...but I HATED HATED HATED memorization... still do, and I am now looking down the barrel of 36. This really hurt me in school. I had a terrible time in math because there were things you just had to memorize...like the times tables. I had a hard time in grammer, because I hated memorizing the 'rules'. I did ok in school... B/C student mostly. But, those things were I really put in some effort... I got A's. If I had put in that effort in everything, I would have been a much better student. But the memorization always got me.
My point is, make learning fun. Just work it into every day life.
My daughter has an alphabet puzzle. She loves puzzles. (she's only 21 months) When my husband and I 'play puzzles' with her and she picks up a letter to put it with the picture...we just say 'that's the letter B' ... or whatever letter is it. It was never about making her learn...but just using a teaching opportunity during something she enjoyed doing anyway. Now, when she's in the mood...she can recognize her entire alphabet.. and say all but a couple of the letters. (W and Q are still difficult for her to say) No, she isn't a genius child ... yeah, she's smart...but it was never 'learning' for her. It was just something fun that we would do. It was playing for her. We never did this so she would know her alphabet before the age of 2. It was just a puzzle my sister got her for Christmas because she likes puzzles and she already had a couple of animal puzzles.
My guess would be that your daughter knows more then she is letting on....but it sounds like you're making it to be work...so she's balking at it. Make it fun. Don't put the pressure on her. Just spend time with her, read books, point out letters, just find fun ways to create learning opportunities doing things she already likes to do.
If learning is perceived as work now ... it always will be to her.