I'm assuming she didnt say this so her friend could hear it. If she did, you just need to judge her friends reaction, which will be more shocked than anythign assume.
It means either her friend is being a bytch, and she feels it would be in her best interest to get nailed. OR, she just got out of a relationship, and being a bummer, and she feels it would be in her best interest to get nailed.Or, it means her friend is cokblocking her from getting nailed, and wants someone to distract her.
Unfortunately, this does NOT mean the chick wants you, and it doesnt not mean her friend is gonna help you in any way. It does mean that at least her friend finds you mildly attractive. You could pry her friend for some inside information about what turns her friend on, though. That will give you an advantage. You could plan a strategy with her friend, like if you and the chick hit it off, her friend just dissapears. "Oh, however will I get home now?? Hmmmmmm."