Walking Away

Hi, I am in a relation with a girl for 8 Years. We are distant from each other around 1200 Kms but we kept talking on phone with occasional meetings! her family was not accepting me but she was trying to convince them. Last time when we met i asked her to try hard, once i will be back again we can sit with them & discuss. In between they found a match for her, however later they found horoscope not showing good signs.But she in the meanwhile met him and found him good, she started talking to him and quite regularly meeting him, as he is only 200 Kms away.I am surprised by the way she told me in 1 month she has started liking him a lot and is into a committed relation with him. I can not understand what to do and what not. I want to settle things gracefully, however i will not be able to withstand loss of her love towards me..can you suggest someway to win her back or to end this relation with a reasonable trust remaining!!