It sounds to me that with her forgetfulness and confusion, it might be time to consider someone being able to assist her in a more formal role.
Does she have an LPA? If not, (and try to put to one side the fact that you think she is nuts), an application for Deputyship may be in order. However, this will depend on whether she actually has capacity to deal with her property and affairs. Just the fact that she is vulnerable though will not be enough.
Has there been any social services involvement?