You are right, it's maggots. You will need to get rid of those asap.
Wash her vent in warm soapy water, this will help remove a lot of them. Then pick off as many as you can with tweezers. Repeat the process. Give her breaks if she's stressed.
Flystrike can be very serious and yes, it can kill the bird in a short period of time.
Once you start cleaning her up, check to see if you can find a wound on the outside of her body or where the maggots are coming from.
Do you have someone that can help you with this?
I'm sorry sweetie. Do the best you can