I would be a little concerned that she may have a learning disability. Don't freak out at those words, because it doesn't mean that she isn't smart, she just may have some issues "processing" the information in her head and there are things that can help!
I would call the school where she will be attending kindergarten and tell them your concern and ask for whomever is in charge of I.E.P.s or who does testing for things like this. Tell them you feel like she may need some help PRIOR to kindergarten and ask for resources.
Another place that may be able to help is DHS. They have what is called Early Intervention where they assess developmental delays in toddlers (0-3) but I bet they know of other programs for older children as well. (I didn't have any luck with my brief search on their site.)
Otherwise, I would continue to stay light-hearted about it and play games. There are lots online, but here are a few that we have done:
For every letter she recognizes (you can do this with words later,) write it on a slip of paper and make a paper chain. For every 3 letters, she gets a prize. The prize can be anything from a little toy to doing a messy art project, etc etc.
Hide letters in Easter Eggs and go on a hunt!
Put the alphabet up in various places around your house or in the car, etc (the dollar store has all sorts of things- foam bathtub letters, puzzles, posters or strips that you can hang on the wall, etc.)
Does she watch TV? I'm not a big fan of kids getting screen time, but a lot of the PBS shows can be good for learning alphabet. Word World is good for repetition and it makes the letters into words that form into animal shapes, etc. Games like "Leapster" handheld games might be fun too for her.
Use playdough to form the words by hand, or alphabet cookie cutters. Have her try to "write" them in fingerpaint, etc. Using multiple senses at ONCE can often be good to help cement things in your mind. Etsy.com has big wooden alphabets you can play with as well as www.souns.org which are big letters to touch with braille on them.
We made our own alphabet when teaching my daughter to read by using water bottle caps (the white screw-tops) and writing on the top with a Sharpie each letter. Then you can play with them and rearrange, etc.
Hope this helps. Feel free to contact me if you need more ideas. I have taught pre-school and homeschooled my daughter for Kindergarten.
Above all, have patience, keep encouraging her, and remember that so soon this will be a distant memory! Kids all grow up fast, but each at their own pace. It sounds like you are on the right track!