You could be right that she may be entering a semi-dementia state. I'd say that if she isn't hurting anyone or herself, then maybe it is best to let her go. I don't know how senior cats handle catnip, or else I'd say to lure her away from her antics with that. It may be safe, but it may be not. Your vet should know. Plenty of playing and attention may also help if her heart and bones can handle it 