You should be using hands-on strategies. Flashcards or books is not the answer.
To teach letters...
Have the child paint something that begins with that letter- apples, artichokes, asparagus, etc. Then reinforce with your alphabet books.
Try to paint in shaving cream in the bathtub, on a tray at the table, etc. Use salt and have you child trace the letter or number in salt.
Practice counting out objects to 5- making a line with them to show her you touched each one and each one is programmed with a number as you do so.
My son has autism and I used a lot of textural ideas to work with him at home. As well, I have taught Pre-K and Kinder for 9 years.
Label her room and your home- particularly those areas where she spends the most time. Likewise, begin teaching her to recognize her name and the letters that are in her name...it's fun and it's more meaningful.
Get a paintbrush and have her use those flashcards to paint with water on the sidewalk- match the letter. Or, you write it and she says the name of the letter....before it disappears!
Use playdough to make letters and numbers. As well, teach her to cut by starting with safety scissors- the metal edged type and playdough. Practice "thumbs- up" and open and shut.
Good luck and have fun!!!
Early childhood educator