IQ tests are very inaccurate for people who have developmental delays & especially those with communication delays.
Learning through song can help people memorize but they don't retain the information in the same way as things learned through other methods. Often things learned through song can only be remembered by repeating the song whereas something learned by flashcards for example, can be remembered instantly.
That's great that you are getting started on the Doman books. I recommend How to Multiply Your Baby's Intelligence as well as the pathway to wellness. I read What to do About Your Brain Injured Child first & it drove me nuts! It is a history of the Doman method & never does get around to telling you "what to do". It is good to know the history but was very frustrating to have to wait for the other books to come to tell me "what to do". I'm sure I would have enjoyed it more if I had known it was just a history.
I would recommend getting a neurodevelopmental evaluation if at all possible. If you can do a program to help organize her brain first, it will allow her to learn the information more easily. Here is a link to the most complete list of neurodevelopmentalists that I know of:
http://dsdaytoday.blogspot.com/2011/06/get-your-own-neurodevelopmentalist.htmlOtherwise, the Doman books will be very helpful at creating your own program & I'm sure the parents here will be able to help you also.