I guess I view the subjects in Glenn's songs as nothing more than someone struggling to get over a broken heart and, therefore, I am sympathetic towards them. We've all been through a breakup and, it hurts and takes time for us to mend. Where I draw the line is that it becomes pathetic and tragic when a person is unable to overcome these setbacks and it becomes a life-long cycle.
Since you feel the girl in 'She Can't Let Go' is doomed to unhappiness, I can see where you would view her as tragic or pathetic. However, I take a more positive view of the situation and choose to believe that she is experiencing a heartbreak from which she will eventually recover. These lines in the last verse give me hope that she'll be okay ...