Story is like this. I want make it simple because my heart very pain now.

I argued with my gf. Then cool down 1-2 weeks. In between the time she blocked my FB and Call. I suspected something weird actually but didnt bother much.
Then today i used another FB account to login and check her FB to found out that she is having another bf now. My heart suddenly pain till F die.

Few weeks ago we just having intimacy sweetly and good, then argued abit and within few weeks she found another bf secretly. You know how pain is my heart now? What should i do? My heart too pain and geram! How can she like that?

The best response is to act cool as if nothing happened.
Give her a cold shoulder, ignore her, pretend she never existed.
Then you will see how she will respond.