As far as I can see, yes, there is a difference. It's sad that these terms are associated more with females, but you know how that goes. Anyway, my definitions:
1. Golddigger: Any individual who associates with/dates/engages in sexual behavior with another individual for monetary and financial gain. This individual will stick around as long as he/she is receiving cash, jewelry, cars, etc... but when the money runs out, chances are they will too.
2. Groupie: OOHHHH these are pitiful. Any individual who is a member of an unspoken fan club for another individual, commonly because of a change in status. For example: Person A just crossed into XYZ org. Chances are, they will encounter groupies who never gave them a 2nd glance before. Because of course, they are NOT the same person they were before - they are an XYZ!

Or... Guy B turns out to be a surprise star quarterback, shocking the hell out of people who didn't give him the time of day before. Those same people can become groupies before you know it.
Just my take.