I certainly feel your pain, I had to go through the same thing with my mother two years ago and I knew at the time it was the right thing to do and I know it today but it still hurts. As the others have said, she knows in her heart you love her and are doing what's best for her. Stay by her side and know you are a good person. Prayer helps too. My father, 92 years old now lives with us and his time is growing short too. Be strong.