There must be more to this story because it does not make sense. Your daughter knows enough to turn the light on and off because you can't hear, but she thinks you hear enough that she does not need to learn ASL?
And, you don't want to get the hearing test because you know it will be worst than before?
I know the hearing test will be hard for you, but if you plan on using sign anyway what is the difference?
I agree with the other posters, take the test and call her bluff.
In the mean time, setup classes with your other two children for night school and go with them to the class. Don't just tell them to take classes because that is not going to work, IMO. Go to the class and do signs with them.