There are many Deans in the hierarchy of medicine. Deans, Deputy Deans, Associate Deans, etc. While Dean is the appropriate title for Dr. Ment, many individuals call her Dr. Ment. (Source: personal knowledge from working with her.) Plus, she's not the type to worry about that sort of thing! It is Director Silverman, but nobody will ever fault you for using a stronger honorific (e.g. Dr. for Mr.; Dean for Dr.; etc.), so I wouldn't worry too much if Dean Silverman is hardwired into your head (although technically incorrect).