Ms. Fix-It: trying to fix every little problem doesn't ever seem to happen.

Its strange. I've never really had any problems with my friends, ever. Then all of a sudden I'm a senior in high school and BAM I'm swarmed. It feels like everything and everyone is changing around me from people I know very well and love, to almost complete strangers at times. I had a friend all through middle school and now all through high school that was just as boy shy as me, if not more so, who suddenly became incredibly crazy about boys, and seems to have a new boyfriend on a monthly to weekly basis. Her morals have changed, her religeon has changed, and the way she dresses have all drastically changed. When this began to happen, I was scared out of my mind. It started out slowly, with her first dropping the faith we both shared to take up some random faith I knew nothing about, which bugged me slightly but I got over it, knowing that religeon is a personal desicion and I shouldn't be bothred by it. But other personal decisions began to really worry me, her easy attitude towards men especially. I felt she was losing her sense of self respect, and was just allowing herself to be used.
I wanted to fix it, I wanted to shape her up slap her in the face or just talk to her calmly and explain to her what a mess she was making out of her life. But everyone I talked to told me no, I'd just drive her away, she'd grow up eventually, and I shouldn't jeopardize a friendship over something that's not really affecting anyone except her. This drove me mad. I couldn't stand watching her grow worse and worse before my eyes and think on the fact that I could do absolutely nothing. Why? Why couldn't I just take her by the hand and show her what she was doing to herself? It made me sick.
The rest of the year continued to progress in this manner, more of my friends began to do things that I'd never dreamed possible or capable of them. The girl I'd always considered to be my best friend became incredibly violent suddenly, and was subject to fits of yelling and punching in order to quell her anger. I fell victim to most of these onslaughts, which to me arose for incredibly dumb reasons. I never was angry, I never get angry at people. But what I brushed off at first began to really eat at me, and drove me to the point that I thought I ought to do somthing about it, get to the bottom of the problem, and try to figure out if something had happend to cause the change, and ultimatly fix it. I talked to her, I did everything in my power to try to fix it. Things improved for awhile, but the old anger would and still does arrise, still comes back in violent force. It's come to the point that I feel I have to walk on eggshells when I speak to her, I can't provoke her, can't anger her, and that is the most half fixed job ever to arrise. =(
Why can't things be fixed? Why are we given problems with no solution, that just eat away at our souls until we choose to either ignore them or let them drive us to madness?