GIRLS, GIRLS, GIRLS: Lena Dunham of HBO’s “Girls” has directed the short film “BFF” for Rachel Antonoff to show off her fall collection. Dunham dates the designer’s brother Jack, who handled the four-minute flick’s music. But the family ties don’t stop there. Dunham’s sister Grace plays a leading role, wearing all sorts of pieces from Antonoff’s collection. Both families will no doubt be represented at the “BFF” screening March 28 at The National Arts Club in New York.