Your starting point for this assignment should be thinking about a rhetorical situation for your assignment. You might choose to write this as a speech which Sarah makes to James on a specific occasion or perhaps as a letter which Sarah writes to her mother. The more detail you add to the rhetorical situation for the assignment, the easier you will find it to compose the assignment.
The essential argument in the assignment should be about the nature of Deaf culture. If Deaf and hearing cultures are different but equal, there is no more reason for Deaf people to learning lip reading and speech than for hearing people to learn ASL. Arguing that Deaf people must make the effort to learn speech essentially subordinates Deaf to hearing culture and defines Deafness as a disability rather than its own unique culture.
A second issue here is one about relationships. Sarah can also argue that if her mother or James want her to change, that suggests that they do not love and respect her as she actually is.