OCD mum's need for constant reassurance

My paranoid elderly mum is constantly seeking reassurance that she will not be locked up(delusion) by my brother and makes comnents like: "I will be locked up won't I?"...to which the natural response is "no, you wont be". Other times she frames a statement like... "you won't give me my meds when he locks me up" to which if I refrain from responding due today avoidance of enabling her compulsive need for a reassuring response, she would push further and say: "that's why I am scared, because you will neglect me and want me to die".... It's very hard tonight not take it personally. "if only you promise you'll let me stay with you forever, then I won't be scared anymore… all you have to do is say yes, then I won't bother yoi again.... ". If I don't respond.... "now I am so scared because yoi won't give me the reassurance "etc.... It goes round in circles. Anybody with a similar experience with a loved one you care for who can give me some wisdom?