How old is your ferret?
The younger the better. Some of the younger ferrets only show symptoms for a few days and then they're as good as new, although they can continue to "spill" the virus for a long time afterwards. So please make sure you do not handle any other ferrets for a while at least not without thoroughly washing your hands and covering your clothing.
Once a ferret has overcome the symptoms it acquires lifetime immunity to the disease.
Feed your ferret easily digested foods like Gerber stage2 turkey or chicken baby food and "duck soup". You can see if she'll eat it on her own but you may have to spoon or syringe feed her for a while.
"Duck Soup" is really just a name for any type of special diet for sick or elderly ferrets. Google it and find one you like, you don't have to get too complicated.
My oldest female was very ill in January and I mixed gerber chicken or turkey food with some FerretVite(a vitamin paste), a tiny bit of Ferretone, cause she loves it so, and Pedialyte. Careful not to make it too thin or your ferret could choke on it if you are syringe feeding.
Here's one recipe I found online
One can Sustacal 8oz (this is non-dairy)
One can water
4oz dry food -soaked in enough water to cover and soften completely
Optional-electrolyte water (really helps-comes in powder form), baby food such as chicken or turkey.
You still need to get your ferret checked by the vet, especially since you have had ECE in your house prior. Good luck to you and your fert.