Oh, do you really think, I will be able to put her down because of blindness!!!!??????

You have a very wrong idea about me. I absolutely agree the quality of life is the most important!!!!! I will do all possible if she can live a happy life without suffering. I don't care blind she is or not, I do care if she is in suffer or not. The reason vet recommends me to do it
if her symptoms not go away, prognoses are bad - she WILL suffer. And blindness is not the reason, pain and side effects ARE.