Hi,
Thank you for sharing your story and sorry that you are in a difficult situation with your sister in law. If you would like some support and advice maybe you would like to contact us at Icarus Trust. We are a charity that offers help and guidance to people in your situation, dealing with addiction in the family.
If you get in touch one of our trained and experienced Family Friends would be in touch and maybe talking with them would help you to know what to do.
You can contact Icarus Trust on help@icarustrust.org or visit our website http://www.icarustrust.org
Good luck.