Given her reluctance to commit to you, you can't be sure that she isn't still holding out for a better deal. She might not be actively searching, but she might be game if something "better" (according to her definition) comes along.
Based on what I can infer from your posts, you seem to be into her more than she is into you. Like others have said, girls always want a catch. It's always the woman that should be asking for exclusivity. Not the guy.
Always keep your options open. You don't have to go and bang a bunch of other women, but you should definitely have some lined up if this falls through. Do that, and you will find that you will be more attractive in this girl's eyes.
NEVER give you heart to a woman until she gives hers to you.
Based on what I can infer from your posts, you seem to be into her more than she is into you. Like others have said, girls always want a catch. It's always the woman that should be asking for exclusivity. Not the guy.
Always keep your options open. You don't have to go and bang a bunch of other women, but you should definitely have some lined up if this falls through. Do that, and you will find that you will be more attractive in this girl's eyes.
NEVER give you heart to a woman until she gives hers to you.