Fleas or not

Please help me with advice this is our first cat with fleas or so we think. In the past year 2 year and a half We rescued a cat from the shelter and ended up passing away from liver failure two months later and then we brought an outside cat inside had the cat treated shots dewormed the whole nine yards gave it a couple of baths and ended up spraying so it became an outside cat again the current cat we have is almost a year old and she\’s been acting different scratching more grooming herself more and usual and avoiding her normal chair She lays in switch to another piece of furniture so I got her flea treatment I put it on her neck kept her away from everybody secluded for 12 hours and thoroughly clean the house and used a spray from the vet let that dry and I vacuum every other day throughout the whole house I did laundry all the bedding everything on hot and I have not found any fleas anywhere in the home or on the cat I don\’t see any of the feces or what people call it the black dirt on the cat anywhere I also have look for fleas on her by her back of her tail underneath her neck by her ears I do notice in her ears she does have some black stuff in there but nowhere else when I brushed her today I found white specks and I looked it up online and determined it\’s not eggs by the shape and sickness it\’s more of dandruff so I\’m trying to figure out what we\’re doing wrong or if it may be something else going on with the cat other than fleas we our self are not getting bit at all so we\’re just really confused please help.