What is your problem? :P Seriously... Put yourself through all this for what? Your not taking any of the advice anyone is giving you.
Yes perhaps the girl has felt trapped in the relationship and maybe she wants to experience different things so she has a chance to find herself before she commits to someone for the rest of her life. Most people I have spoke to who were in a relationship at a young age well it never lasted. Those who married regretted not having a 'wild stage' as such. Some people need this to find themselves, others don't. But we all have to do some soul searching at one point. So give the girl space and move on with your life. She's not dead is she? Get yourself a new happy life with new and refreshing things to do, take a holiday... do something but get yourself away from this soul destroying situation.
My mum married when she was young and it lasted 6 years before she met my dad at 30. They actually remained friends and he was always around me and my sis as kids, don't know how my dad dealt with it... Very strange situation as I look back to my childhood. They probably never speak now really. She's 52 now.