A goth nymphet is more darker than a grunge nymphet they wear more darker colors and heavier make up.i would take inspiration from the movie the craft or Wednesday Addams from the Addams family
Actions/Mannerisms
Sneaking out late at night
Quoting scary movies all the time
Having an emotionless expression
Having a dark sense of humor
Being very blunt
Being sweet to the people you love
Fashion items
Chains
Chokers
Ripped fishnets
Ripped jeans
Ripped shorts
Band t shirts
Skirts
Crop tops