Second Language Aquistion and the maturational state hypothesis

I found this topic to be extremely interesting mainly because one of my best friends has experienced the development of several languages over the course of her life. Her first language and the one that she speaks at home with her family is Farsi (the language spoken in Iran). When she was two she was relocated to Italy where she learned to speak Italian almost fluently, later when she was about seven her family again moved to the United States where she learned to speak English. This is the language that she speaks most because she had been in this country since then and uses it on a day to day basis. She then learned Spanish in college. Although she speaks English extremely well and most people would think that it was her first language, she still has some interesting grammatical mistakes which I find to be fascinating. What I also find to be fascinating about her story is the fact that English is the only language which she can read and write fluently (she does fairly well with Spanish however this is a newly acquired language). She also no longer remembers how to speak or understand Italian.
After reading the Johnson and Newport article on critical periods of language acquisition I felt that the maturational state hypothesis seemed to be more supported by this particular case study. I feel that the fact that she was able to learn so many completely new languages in such a short span of her life shows the ability of children to adapt their language to the environment in which they are in. Her brother who is only four years older than she, never learned Italian and still has a very thick accent. I find this to show that children really do have a critical period in which they are able to learn language, and learn it with ease. I felt that the exercise theory would be hard to prove because of the fact that so much research has shown that adults have a harder time learning a new language, even if they live in a new country. My friend's parents for example still are not very comfortable speaking English and they have been in this country for a very long time, and know English. I relate it to when I was learning to speak Spanish and even though I could understand what was being said I still was not comfortable converstating.
I feel that this critical period could be used to better improve the way in which ESL students are treated in schools. My friend had a very difficult time adjusting when she first came to this country and I feel that part of it had to do with the insensitivity of our school systems when it comes to non native English speakers.