[Note: I initially asked this at the Linguistics community, but was suggested to try here.]
I have an adult friend who was born deaf. While I am very slowly learning sign language, we generally communicate (in Japanese) by writing messages to each other. Recently, she has shown an interest in learning English. She wants to write English; speaking and listening is not very practical. Whenever I teach her English words, she asks how it is "pronounced", which I approximate the English sounds with Japanese script (katakana). The Japanese language, though, is phonetically much simpler than English and makes a very poor approximation.
I graduated with a minor in general linguistics so am quite familiar with IPA. IPA is a fairly ideal system for expressing English pronunciation. It is also used by many ESL text books, too. However, as my friend is deaf, I am unsure how to teach IPA to her, or even if it could be a useful concept.
I am wondering if IPA can be of any use to a deaf person, and if so, how it can be taught / learned.
Edit: I realize that this question is likely difficult to answer. I would be interested in reading about previous studies / cases if they exist.