Pamper her.. girls like being pampered.. tell her she means the world to you.. tell her how beautiful she is.. take her out for a nice dinner.. buy her flowers and chocolates and lots of gifts.... make her feel like she is the only girl in the world (like rihanna says)... she'll come back. If she doesn't, then tough luck... move on.. and find a new girl... and treat her better this time so that she doesn't leave you for a stranger like this one!

It is very difficult to say if she loves you or not without hearing her side of the story.... just because you were together for 5 years doesn't mean she was happy with you.