MIL HELP!!

My MIL has never kept our toddler over to stay the night. 1) She has never had a stable home 2) She has abused alcohol and drugs for a long time but says she is sober now 3) Moved 2 hours away to a different state to get sober and live off of her parents 4) Always makes comments about how our child is raised around technology and how we raise our child. 5) Makes comments about my choice to be a stay at home mom and that it's unfair to my spouse. Let me be clear that she is sweet but she also is bipolar and has had issues with suicide and abuse. She has been through alot but has also put herself through alot. But now she is insisting on keeping our child over for 2 nights 2 hours away. I dont want to hurt her because when you tell her no she guilt trips you. I would fear for my childs life if she was ever alone with her. I hate to have to be the bad guy and my spouse just doesnt care anymore. She is consistently guilt tripping us for not seeing her grandchild. But it's NOT OUR fault she moved away to get sober. It's not our fault that when she lived near us that she chose to binge drink and do drugs and put herself in the hospital for months. We let her come visit. But we refuse to let our child stay with her. How do I go about telling her I am not okay with it but so that I dont push this emotionally unstable person over the edge. This is a REAL problem. I need REAL advice. How do I deal with an addict mother in law?