Are you certain that the private school accepts no federal funds in the form of program assistance? If they do, then the OCR in Boston will help, otherwise the OCR has no legal authority in a private school.
Do you have a clear understanding of the amount of work in the English classes that is expected to be completed via email? If so, and your daughter can manage it, agree to this solution.
If the private school is a religious one, then it does not have to comply with ADA requirements. If it is not, the only thing it must comply with is a reasonable accommodation. The offer of graduation with completion of courses via email is what the school feels is reasonable. With only 1 month left, it may be best to accept this offer.
I wish you and your daughter the best of luck.