She date with me but didn't told me she already had boyfriend. What should I do ? ?

I was been abandon by my ex-girlfriend about 18months ago. I was so down & desperate. Getting crazy & no mood to work at all. Then about half year ago, I am going to oversea for work. Then I met this girl. She is from local She is nice, cute & a very good companion. She always can speak right into my heart. Then very fast we getting close. After 2 months our relation already very close. Then about 1 month ago, she said want to leave me. I refuse & keep asking the reason. At first she told me that her mother don't like me. But after ask & ask, she confess that she already had a boyfriend before me. Their relation already 5 years. She said her boyfriend found out our relation & say if she leave him, he will rather die. She don't want to hurt him so She told him that she will choose him. But she told me she is more in love with me. I told her since I am a late comer, I choose to retreat. But until now i still keep missing her. At the same time, my heart still feel very chill & pain as cheated by her. Now she time to time will call me. During our talk, she occasionally will cry & saying that she love me. I really don't what to do. If asking me to let go, how can I do that ?