Honestly, ( AND THIS REALLY REALLY ISNT A ME-LIKE ANSWER), I would do something.....Maybe not turn her into the school, but ground her azz for the first week or 2 of summer.
Listen to this. First of all....if she wasnt gonna pass her MIDDLE SCHOOL MATH FINAL without cheating, she has a long life of failure ahead of her in highschool and college, so u shouldnt let her think she's always gonna get the B or whatever
As a kid who sometimes cheats in highschool (not on finals....ok fine on finals a little

) Ive gotta say school was too damned easy in 1-8th grades for me, and i never learned a work ethic at ALL, except for the rare assignment that interested me when I might spend 5 hours when 1 hour was necessary. Now im a junior (well...senior now) in highschool, and oh crap, THERE IS NOTHIGN INTERESTING, so i get C's and D's while mental midgets and bimbo's slide by with B's...just cuz they spend 2 hours doing dumb spanish homework every night.
Anyhow, the only thing that has carried me this far in highschool is that im smart enough to get B's on basically all of my tests in honors classes without studying or really paying attention sometimes. If your daughter is having a hard time in middle school...good god....get her in gear now rather than later...she's gonna have a hard time