We need your advice

lucy Angel- 18/7/97--10/- 7/2011

For Little- Bit...DIE CANCER- DIE
Barked: Tue Feb 26, '08 2:47pm PST 
We have been off line for very long since mommy works all day...
Recently we have been fighting for MAron's life.This morning we got her blood work results and the news are very bad.
To cut a long story short, Maron has lost dramatically 11 kilos in less than a month.She has diabetes, renal failure, liver defeciency, pancreatitis that comes and goes.Iit seems that nothing works.She is the bravest pup at the vets while taking her medication.Today the vet told us that she won't live for long.She doesn't bark anymore, she can't go for walkies and she woobles all the time when she tries to move.
We are in tears while writing this, When do you know when is the roght time to let your baby go?How can you take this decision when you see her wagging her tail at you sight?
Please give us your advice.We don't want her to suffer and we can't let her go!