Let mom visit her sister for the weekend, now they wont bring her back home. What now?

Ive been my mothers caregiver for the last seven months. She suffered a brain injury, so her twin sister as been a real evil person in soour family, so she asked if my mom could visit her for the weekend, they live two hours away.so I said yes, well now they wont bring her back and say shes the one who doesnt want to live with me anymore. What are my legal rights?