Anxiety and paranoia

Hi everyone, I am new toy the forum and would like some advice on how to deal with my elderly mother's delusions. She lives with me and my husband and child. She normally goes to my brother's house on weekends to give me and my family a break from care. She does not have dementia, but have always been an anxious person who has suffered with anxiety and depression on and off over the years. We lost dad suddenly in a traumatic fall at home nearly 2 years ago. Recently, she had a relapse of her anxiety and depression but this time, she has delusions that my brother has intentions of taking her away from my house to live with him and his wife permanently and that as a punishment for being "difficult" and nagging, would be locked up in their apartment all week with not food or medication while they go to work. No amount of convincing eases her paranoia. Now she wants to stay with me 24/7. Admittedly my brother did suggest that she could live with them if and when things got too hard for me to manage, but certainly would care for her needs eg food and meds etc.... I am worn out with her constant demands to stay with me or to find ways of getting her out of the "prison" at my brothers such as ringing the police if he doesn't bring her back to me at the end of the weekend..... How to break in if she's locked in etc.... My brother was hoping he could offer me help rather that locking her up and now, she is paranoid of eveb leaving my place in case he finds her and "takes her away"... She is taking medication to help with anxiety and delusions, but the recent increase in dose might take a couple if weeks to kick in. How do I cope in the meantime?