How to retrieve a car gifted to sister without conflict?

I'm in tears as I write this, feeling deeply unlucky. I can't help but wonder why God has chosen this path for us. We're facing a tough situation because our cousin sister married into a family full of narcissists. Her husband is especially difficult—he’s narcissistic and a psychopath. We gave our sister a car as a gift when she came back home after suffering a lot with them. Now, we want to take the car back, but we don't want to make things worse for our sister by involving the police or going through a divorce. We're a simple family and never expected something like this to happen to us. The car is in my brother’s name, and he's the one paying for it. We don’t want them to keep using it because of everything they’ve put us through. Our main goal is to protect our sister's peace of mind and help her recover from what she’s been through. So, we’re looking for the best way to get the car back without causing her more stress.