Psychology is a field that has recently seen a feminization, meaning that more and more women are getting into the field. If you think of the generation the Freud existed in as the initation of psychologists then please consider his daughter Anna Freud went on to have a successful carreer in psychology. Generally the initial theorists are most men however, I don't necessarily believe women were ever "not allowed' to study psychology but rather that it wasn't a common thing for a female to do in that time period because of the way we viewed gender roles.