Hi, Good Afternoon Me And My Girlfriend Are Making Relationship

Hi, Good afternoon me and my girlfriend are making relationship from last 6years. Now due to completion of our education we went long for couple of months, now she was doing in a reputed software company. After getting into job i saw many difficulties from her side one day i asked her, what's going wrong with you? Then she replied me that she was in a relation with her colleague and they are mingled at one time. But now question is she was still saying that she loves me more and more but past was happend accidentally and i wont repeat it agian i will be with u forever and ever.. Now my main problem is will i accept her or not?? If i accept our lives will be happy or not??? Please suggest me.