Girls who you are friends with and involve in your social activities, but mainly because they are girls, and moreso for superficial than real redeeming qualities. Often called upon to help achieve a 1:1 male-female ratio. Can also be used in reverse, to describe males, although that is less common.
"Want to see if Liz and her friends are interested in going downtown tonight?"
"Nah we have 5 girls already, we don't need any ratio fodder"
"She's kind of boring but she's hot so she makes good ratio fodder"