What can a person do with a PhD in Mathematics besides being a college professor?

My friend has a Master's degree in Math & wants to further her education & do something other than teaching. What can she do? What do mathematicians do in general? Also, she has an undergraduate minor in Psychology & Spanish & an undergraduate dual degree in Math & English. Since she has these lower level degrees in other areas, does she HAVE to get a PhD in Math or can she get one in Psychology? Does she have to get a 2nd Master's in Psychology? She has a Master's degree in Math but wants to pursue a PhD in Psychology, since her job is Psychology-related & she's more interested in Psychology. She wants to be a clinical Psychologist. Can a person get a job that's linked with Psychology & Math together? If so, what career fields?