Bright child can't retain letter names?

Did she know her letters at some point, and then forget them, or is she still in the learning stages? With Dennis, we used the whole Leap Frog system. The best was the "Letter Factory" video, which had a song and a mnemonic learning device for each letter. Dennis loved it, and he still remembers that a K is for kick. Just a suggestion. What does her preschool teacher say?