Discussion on the following website may help you make THE difficult decision:
http://veterinaryteam.dvm360.com/firstline/data/articlestandard//firstline/152009/591813/article.pdf

Sometimes the decision to end a pet’s life is “black and white,” such as when they are in great pain, not eating, etc. But, often, we are left w/ making the decision based on what quality, or lack thereof, of life the pet is leading.

Consider what things s(he) enjoys the most. When they are no longer enjoying them, or when the pain level, as you perceive it, is too great, then you can love them enough to let them go.

Our pets are left w/ some of their natural instincts – bark when a stranger approaches, wag your tail for a friend, and hide your pain. If one shows weakness, other creatures can take advantage and kill you. Our pets do not consciously think, “oh, if I cry, someone’s gonna eat me,” but, rather, those animals who were quiet during painful episodes, went on to reproduce. That’s why we have to try to put ourselves in their place and consider how we would feel if we had the same disorder.

I wish I could say that I always “know” when the time is right to have my pet’s life ended humanely, but, in reality, I suffer the same pain as everyone else when forced to make the decision. One thing I will say is that I ahve come to the place that I’d rather “end it too early” than to make one of my pets suffer, just for me.

We, as the advocates for our pets, need to set limits: limits on how long we are going to allow the pet to suffer, limits on the physical cost to the pet, emotional limits for our family, and yes, even financial limits. And, sometimes we have to love them enough to let them go.

Go to  http://www.rainbowbridge.com You can add your dogs name there, and every Monday night they have a virtual candlelight ceremony. It’s very comforting to be connected with others that are also grieving. Never lose your faith and continue having and showing the utmost strength for your Sophie. We ride this darned roller coaster with all our ME babies during their stay with us. They can always “read” your feelings and actions, so important to try hard to find the joy of the moment Sophie brings to your life. Every decision is extremely hard and know the stresses are beyond what most folks can ever experience, but stop, breathe and try to make the most of each precious minute.

Always weigh the quality of life. Someone once posted we should ask if there are 3 things your baby loves to do right now and can still manage with your kind love.  Make sure you do everything you can and are able to do so there are no regrets.

God and Dog
http://www.youtube.com/watch?v=H17edn_RZoY