Hi,
I'm in a similar situation as an international student. I got accepted into the MPH in Epidemiology and I tried to get a GA position but I've not secured anything.
The members of staff keep referring me from one person to another.
I don't know if you listened to the online conference on "Funding your GW education", but apparently many MPH students use personal (or family) funds or apply for loans.
I know securing loans can be very difficult for international students. So, I have almost given up on getting funded through the program and attending GW.
You may try calling the program. May be they will have an a definite or better answer for you.