Should I give her another chance?

I was on my Ukraine ski trip with some businessmen for the last two weeks. The two-week trip was all for work. While I was there, I thought of surprising my girlfriend. There is no special occasion; I just want to surprise her with flowers and chocolates. On our way back, I bought her gift-- a Gucci bag. I just miss her so much, that's why I did that. When the plane landed at my hometown, the very first thing I had in mind was to visit her at her workplace and so I did. When I arrived at her office, I saw how busy she was doing her paper works. I waited for her to look up at me. When she did, her stressful face lighted. A smile curved on her lips and she rushed out of her chair to hug me. I gave her what I had in my hands and kissed her in forehead. However, what caught my attention the moment I look at her after the said kiss was a pair of eyes with tears pooling around it. I asked her why and she began sobbing. I hugged her until she felt relaxed, then she started talking to me. She said she got drunk and had a one night stand with a stranger while I was away. I was dumbfounded. I walked out of her office. She called me but I continued walking. I felt betrayed. She loves me; there's no doubt in that but I am hurt. I know it was a mistake but I can't accept what had happened. I still love her with all of my heart. Should I forget about it and give her another chance or not?