Well, every person has their basic ideal of a relationship. Things they ‘want’ or ‘require’ in a relationship. When your together for two years, she must have realised one of those ‘requirements’ fell short in the relationship. Isnt there anything she may have mentioned over the last two years, things she would like differently? I dont believe that after two years you just fall out of love. You realise something is missing. A person can’t end a relationship after one weekend of doubting. Something has been on her mind a lot longer.