The age can be a factor too. Not all 2nd graders are going to learn the notes that
quickly. I know because I have taught enough of them. What you can do it teach
your student Twinkle, Twinkle Little Star without the notes an any C note on the keyboard. Have your student learn to play with the RH and then the LH separately and then HT. She may love it and no one gets frustrated. Then I teach where middle C is on the keyboard and use a simple
Primer level book. The young student can't handle the skips , not until later on. As long as they
know the middle C, D and E for the right hand and the B and A for the left hand, that should suffice until they comprehend what those 5 notes are and where they are located on the staff lines. I'd forget the flash cards(I never used them, don't do any good, and not the slogans either) with your student. Make sure she is relaxed and is enjoying herself and then the learning the notes will come much easier.
best wishes,
go12_3