What am i supposed to do now????(need a fast and effective suggestion) plz suggest fast. plzzzzzzzzzzzzzzzzzzz?

i love a gul and we two are best frens. we are frens for 2years. about 8 months ago i confessed my heart felt infornt of her. at that moment she just gave me a smile and ped me. i took that smile positively. later she came to me and said that lets continue our relation as a frens only. well as general thought i thought she wants to hav good frenship wid me 1st as every relation is based on true frenship. i was happy for her reply. now time ped on and on. during the time period i usually gave her hint how much i love her and wats her importance in my life. in reply to my actions she also reacted accordingly. it felt as if she also had same feelings for me. even my frens used to say that she likes me too. but about 3 months ago she called me to her place and she told me that shes got proposed about a month ago and she has accepted that proposal. now plz tell me wat am i supposed to do. i love this gul truly and shes my lifes first love but now having known shes wid other person it suffocates. i changed my self for her( from a bad guy to gud guy) but she dint realise my effort to hav her in my life. still we are gud frens but recalling all those time i had wid her and the fact that shes now in relation wid a new guy i cant face her. so i usually ignore her while i meet her on the way. so plz suggest me wat to do im in real big tension. if she never considered me more then a fren then y did she reacted as if she also had same feelins for me???? plz do suggest fast im about to go nuts. plz help fast.. plzzzzzzzzz