In times of pain, namliam, consider this thought.
When you think of your sister-in-law, at first there will be pain and sadness. You will naturally think of her as she was in your most recent memory, which is as she was in death. As time passes, you will be able to look back at happier times and appreciate her life for the joyous experience that it was. When you can look back and see her in your memory as she was in life, you will be able to smile again.