Well if the guy gets busted they wont bust the grilfriend too unless they have proof she new about it. The only way it would realy end up involving her is if they start living together becuase the pigs will just assume she knew if they are living together. If shes clean though of drugs and they do end up living together if the crops outside and not some huge underground pot industry she can easily play dumb with out suspicion IF shes clean thats what the cops will use to see if shes involved.