Children at the middle level have to determine and learn what makes a peer a friend and how to get along with others. Instead of putting your daughter's new friends down, I would suggest that you ask her with genuine interest what she likes about them. Let her talk. Get to know them. Let your daughter invite one or two of them over after school for snacks, to listen to music, or for some girl talk. Not only do you get to oversee the relationships, but your daughter gets to learn about them in a protected atmosphere.
If you are accepting and open with your daughter, she will tell you if these girls really are bad. If she determines they are not true friends, she will stop associating with them on her own as long as she knows you are respecting her decisions and not going to say, "I told you so."