Terminal 8

My wife is flying in from Dubai via Emirates to final destination being Toronto via American Airline transiting via JFK. I cannot get a clear answer from the airlines. Although it is one ticket they think that her baggage is only checked to JFK and then she has to through immigration/customs and take all her luggage and switch the terminal with her luggage to Terminal 8 to AA counter and then recheck-in. Sometimes they say after going through customs she can check her luggage within same terminal ie 3 to connecting flight counter and then change terminal without luggage. If she has to take her luggage then can she grab trolly and take it with on the airtrain to terminal 8. So confusing....