TouchAndGo

So I've got this dilemma where I broke up with my girlfriend with whom I've spent my last 4 years mainly because the relationship was getting boring for the past year or so. I tried to revive the fire, but in vain. I stuck to her cause she's a great person and moved abroad to the same university to be with me when she could have opted for much better offers. She's really kind and thoughtful and was putting much effort in the relationship but I just couldn't bear with it, and ended it 2 months ago.
She was completely devastated, pleading and begging for me to give her another chance, but I tried explaining her that I've tried my best so many times to make it work, and it just didn't. Being with her for 4 years has created some kind of bond and I'm feeling really REALLY bad for what she's going through, but I just can't stay chained to this unrequited love forever. It keeps me awake and makes my heart ache thinking about her throwing away her life because of me. She comes crying to me sometimes, telling me how she can't eat, can't study and cries herself to sleep and starts begging again. I really care for her as a good friend, but sadly not as a partner... Friends are trying to tell her to let go but she says she simply can't. I don't know what to do and it's affecting me and my studies too. I've taken up drinking to ease the pain away. My unit controller has even phoned me, asking me why I've missed the last 4 weeks of tutorial. I'm really lost right now and bad thoughts are running through my mind. What the hell should I do? What does she expect from me? Force my feelings or lie to her? Please help me out with some words of wisdom...