So, girls of reddit...I'm gonna call on you now...

Last night, I was sat down by my girlfriend of three years, and was told she had cheated with a previous boyfriend from high school. To give perspective, were both 20, both have full time jobs, and have been recently attending college together. Her excuse for what's happened was 'I feel I found myself in you, yet also I lost myself.' To some degree I can see this as the case as I too have been feeling 'content.' I am still hopelessly in love with this girl, and honestly need advice if moving on is the right path or not.