Drug addict

How would y'all feel if your fiance was trying to let his drug addict mother stay in your house, while you have 2 kids? She says she "wants" to get clean, so I told her I'd help her find a rehab or she could take and pass drug tests to stay with us. She literally doesnt have interest, but she and my fiance are still trying to get her to stay in our house. What should I do?