I never had ferrets but both eyes being swollen tearful and itchy sounds a lot like conjunctivis. She needs to see a vet, your brother will probably need to put eyedrops in her eyes - it won't be fun (my dog stupidly scratched his eye just two weeks ago while running around and I had to clean and put eyedrops in his eye every 2 hours for 4 days - it was hell, he started running as soon as he saw the bottles especially for the antibiotic which apparently stung a bit XD).
I wouldn't wait. This kind of eye condition is generally treatable in a few days, but when you leave a possible infection fester it can end pretty badly.