Dom,
I would not ever want to do this to any family member. And I am sorry you lost her. You were wonderful to her. Animals tend to feel our energy and unlike humans to live are better at living in the now. I think that all the time you spent with her since bringing her to your house made her happy. Your being with her as she went off to the rainbow was probably the best way to leave. I hope you can remember the good you brought to her more than what you felt you did not.
Magda