I think the idea about restricting the amount of times she can see her friends is a great start...I know it may be hard on you and you may never hear the end of it, but especially after failing so many subjects I wouldn't be allowing her to now that it is holidays "have the run of the house" so to speak. In my mind there has to be some consequences to her actions and I hate to say it but I think you need to follow through on these especially considering the amount of money and the sacrifices that you make for her schooling.