you might have to treat your yard. we had to last year. our vet recommends frontline but we still had the issue you are dealing with last year. treating the yard fixed it.
"washing it off" stated above. not true. call the manufacturer. you shouldn't bathe for a few days before or after. after that recommended time you can give them a bath!
Time to take her to a groomer, get a flea and tick dip. Then to the vet and get some frontline, after being checked to make sure she is ok. Do so asap!
you may want to try a competing brand such as advantix or frontline. your area's fleas may have gotten used to the advantage.
Um, you are WASHING IT OFF every time you bathe her every WEEK! Duh! It's not working because you're washing it off, and don't give two months worth in one month, that is very toxic.
Your backyard should be treated.
When fleas are at their worst you can use the advantage and capstar. Check it out, it's amazing and safe. You can google it and get it at your vets :)