I agree that this is a form of bullying. I would almost bet that this girl is destroying other kids' utensils -- and who knows what else -- and though they may all "think it's cool," they more likely are saying that because they fear standing up to this kid, and they want to placate her.
Go to the school and ask what level of supervision is or isn't going on at lunchtime. Is there an adult monitor in the room during the entire lunch period? Teachers no longer sit in on lunches but most schools have some form of adult supervision, however minimal. I would inform the school that you are aware a child in this class is destroying items your child is bringing in at lunchtime and you want to know why the adult supervision is not better. That may goad them into checking it out. If your daughter is one of several kids to whom this girl is doing this, the kid will not necessarily know that it's your daughter who told what's happening, or you who called the school. (And I would not just call -- schools can easily fob off phone calls. I would go in person and say you want to see the administrative person in charge of the cafeteria. Tell them you'll be checking back in with them within one week of your visit, too.)
You need to give your daughter, meanwhile, many more tools to deal with this specific kid and with other children in general -- both friends and foes. I'm not sure why she doesn't make friends easily; you don't mention if she's just shy, or doesn't have the same interests/activities as most of her classmates, or if there are other reasons. But she could use some good kids' books about standing up to bullies and about making friends. Talk to the children's librarian at your local library and especially to the school librarian. I'd do it without your daughter there, and check out some good fiction as well as nonfiction books about dealing with bullies, making friends, and/or feeling socially awkward.
You also could talk to the school counselor and ask if he or she will meet with your daughter a few times and work with her on whatever she needs like social skills. The counselor can frame it as "lunch with the counselor" like it's a privilege or whatever. This is what the counselor is there for. Helping your girl deal with this now, before middle school, is important.
Also, go to the American Girl web site and check out their excellent "A Smart Girl's Guide to..." series of books. They have one on "A Smart Girl's Guide to Friendship" that may be helpful and many of their other books could be good for her too. These are exactly right for her age and give girls a lot of specific thiings to say in certain situations, and help girls think through what a real friend is and is not.
Finally, is your daughter in activities outside school? If shes' trying to make all her friends through school and is running up against cliques or bullies, consider finding activities for her outside school. Girl Scouts is excellent and any good leader will ensure that all kids are accepted and treated well in the troop. If your child is interested in art, find an art class at the community center or an art center; if she likes books, there are kids' book clubs often run by the local libraries; if she likes to move but isn't sporty, try a dance class (be sure to get a low-pressue dance studio and not one where the emphasis is on being on a competitive dance team etc.). Just some ideas to maybe get her outside the school circle if she isn't already.