I think two factors might play into this
A) obviously you're smaller so you don't need as much to feel bad
And
B) if you are ingesting less sodium then BINGO!
of you ate more sodium before obviously you retained more water do you got less dehydrated since your body had more water in it so now if you don't have much water weight obviously you get dehydrated quicker wich means=worse hangovers.
Just my two cents
I try now to drink 1-2 cups of water at least an hour before I start drinking and my hangovers are actually non existant