Is she a druggie?

Ok so my new gf just told me she smokes weed. We're both 23 and I've never done any type of drug so I'm like scared she's hardcore into it or something. She said she smoke about "a joint a night". Is that too much?? O God does she need some kinda of intervention?? She has a professional 8-5 job, will she get fired?? Please help!