Groups are tough at this age. We have this culture that places so much emphasis on the "BFF" - which is 1 person. You put 3 kids into a group (or 4, or 5...) and the competition begins.
She doesn't want your advice - that is typical. Kids at this age are branching out, starting to assert their independence from parents, which is good prep for "leaving the nest". It's also why you may start seeing more defiance and more secrecy/distance. It's normal, and you need to embrace it as much as your momma instinct kicks in and tells you to fix it! (My kid is in his 20s and I still hate to see him hurt!)
Empower her to make the necessary changes. Help her brainstorm a little on what makes a good friend, what qualities she admires in general, and whether the people she hangs out with exemplify "friend" attributes. Keeping in mind that she is learning, and so are they, to sort out and separate from "childhood" friends to "teen friends" and later to "adult friends", let her know that friendships are like clothes -- you try them on to see if they fit and if they make you look the way you want, and sometimes they are immediately a bad fit, and sometimes you outgrow them later. Just because someone is in her math class or on her sports team doesn't mean they are a good fit. Now, the mean tricks - that's childish, and it's a way for an insecure kid, Friend A, to cement their relationship with Friend B by joining in on making fun of Friend C. So it tells your daughter a lot about Friend A and Friend B if they gang up on her. She has to be the one to decide, though, how many chances she wants to give them to learn from their experience. But she should also look around for Friend D, the kid who isn't in the group and isn't playing tricks and isn't clicking with A or B.
Kids this age don't really know who they are, so they don't know who they want to be with either. I think I'd tell her it's a Great Life Experiment, and she has to be the one to put it through various trials to see what is successful and what is not. That doesn't mean she needs to blackball or badmouth or accuse of bullying someone who isn't kind, but it does mean she can keep her distance.
I think if you encourage her to make her own choices, that's great. But she doesn't get to complain constantly to you if she's not sharing and asking for your help. If she wants to be empowered to make her own choices, great
Remember also that kids are at vastly different places at this age - some are still kids, some are mature teens, and some are vacillating in between. That's why you see so many kids being the "odd one out" on any given day. The hardest thing for you is to give her a couple of things to consider ("How do YOU feel about someone who..." and "What do YOU think you want to do about it") and then step back and let her work on it.