Only she can tell you if she wants an exclusive relationship. And if she does want one, she could be waiting for you to bring it up.
Best way to broach the subject is to ask her - broadly speaking - what she's looking for in a relationship right now. If she says she's looking for exclusivity, then consider broaching the subject. If she says she's not looking for it, then you have your answer.
But most of all, if you wait around for someone else to make a move, you'll get nowhere in life. Life involves risks. Be prepared to take risks
Never regret anything that has happened in your life. It cannot be changed, forgotten or undone. So, take it as a lesson learned and move on.