Betty Co-ed is a character that appears in the 1931 Screen Song "Betty Co-ed". She has a perfectly round head instead of Betty's oval-shaped one, and rubber hose arms and legs. Betty Co-ed is a flapper girl who's loved by every college boy.
Betty Boop's name most likley comes from the Screen Song "Betty Co-ed".
Betty Co-ed is not the same character as Betty Boop more or less a prototype.