sorry to hear that your bird isnt well, and annoyingly so that you cant get the dusting powder. You could try giving her a bath, i gave one of my hens who had lice a bath with gentle baby shampoo ( she was filthy) and then blow dried her and such she stayed inside over night for good measure. next day i checked her for lice thinking that i would need to powder her but nothing, they had all died from the shampooing. If you cannot get something in the next day or so then this might be worth a try. I realise that with bathing a sick bird it can be dangerous but if careful then it is usually fine, just make sure they get a towel dry then a blow dry till they are completely dry and a stay inside over night.