ghost drinker

someone that doesn't need to drink a lot to get drunk at a party; someone who drinks so little that by looking at the bottle, no one can tell they got drunk off of it; 2 or 3 shots and they're out

Brian: Hey did you see Janice at the party last night, she was plastered
Vince: Yeah and she only took a couple shots
Brian: HAHHA she's a ghost drinker