Laura,
i am so sorry to hear that cosmo's problems are getting worse. i thought about you on october 24th as i had to put my sweet little black pug, gomez, down after 13 1/2 years of great life. i haven't been on the forums lately either, and was wondering how cosmo was doing. while gomez' passing is so fresh, it makes me cry to think of what you are going through.
a friend of mine helped me to realize that though gomez was not in any pain, he was suffering mentally because he could not do the things he wanted so badly to do. gomez was wearing diapers , and he would fall on the floor and not be able to get up. he cried all the time because he just wanted to follow me around, and he couldn't. his backend was just gone. making the appointment just about killed me, but i took the next day off to spend with him, and he walked into the vet's office on his own, and he was so brave. i stayed with him to the end and it was hard but i know he was at peace and never had to be helpless again.
i am not trying to divert the attention of this thread off of what you are going through or upset you by saying all of this, but i just want you to know that i, like others on this forum, understand how difficult this decision that you will have to make is. you have done so much for cosmo, and she knows it. when the time comes, just remember that she will again be playing and running around like she did as a puppy.
anyway, i will keep you in my thoughts and will do some more crying of my own for you and for myself.
gayla