I work in a low income neighborhood school as a kindergarten teacher and most of my students come in not being able to recognize ANY letters or knowing how to sing the ABCs at all.
We go ONE LETTER PER WEEK. So for five days in a row we will sing songs related to an "alphafriend" thats related to the letter of the week. Like for S we have a Seal with a name that starts with S. We sing about how he likes to Sit in the Sand and See Sail boats. You get it. Its so they hear the S sound and get familiar with associating the letter and its sound, etc.
Anyway we sing, paint, and glue and practice saying the name of the letter and its sound. Basicallly everything and anything that revolves around that letter for a certain portion of our school day for a whole week. If they dont get it after that week, it would be suprising. They wouldhave to be absent frequently or have maturity or attention issues.
Anyway, we continue on this way until every letter has been taught (yeah thats 26weeks) with time to review in between . Then we move on to digraphs like th, sh, ch, wh, etc.
Developmentally, that is the pace that kids in the 4 -5 range are at. (with a few exceptions of course) IF in two weeks, she only knows two letters well then that sounds about right for where she is developmentally. She'd be normal for a four year old so dont go freakin' out. Your going to have to lower your expectations a bit. Four year olds dont learn like adults do or like older children do.
So starting Monday, introduce your first letter and stick with it until Friday. Since you only have 1 child and I teach 20 kids, you can start with the most important letters to a child: the letters in her name! In a class full of kids with different names we can't accomodate everyone so we just pick S,M,R,T,B,N,H,A, and go from there until all 26 are covered. The letters in a child name are HIGHLY motivating to learn.
Gestures are important with young children. Trace the letter in the air as you sing a poem/song about the letter-of-the-week. Have her copy your gestures. Once, she learns how to copy your gestures and the poem/song. Give her a fat pencil and sing the song again only this time write it on paper as you sing instead of tracing in the air.
Of course practice singing the ABC song, expose her letters using different mediums, get some letter cards or magnetic letters and have her put the letters order according to the ABC song etc.
A fun arts and crafts activity (that also reinforces fine motor skills) is to take a marker to a piece of paper and make a big letter on it then have her glue cheerios onto the black marker. So in the end there is a letter made out of cheerios or rice or beans. Put it on the fridge.
Continue on with as many letters as you have weeks left before she starts Kindergarten. Oh by the way, thats how we teach the numbers too! One number per week.
A great helper for you will be found here:
http://www.edutunes.com I recommend her Phonics Time program. The track called "ABC fun" is great. We use it to supplement our curriculum. The kids love the songs and the gestures we make up for them.
Also, go to http://www.fonts4teachers.com/site/products.cfm
and buy the simplest package the 10$ one. To help her write her letters and numbers.