Well, let's see. You love your girl, you're been together for a while - let's say for 4 years, like in this story - and you propose. Because you love her, you want a family with her and you want to spend future with her. She turns you down and gives you an excuse that she's not sure, she's not ready, or something else. Unless it's something really important, like law-related or immigration-related, I cannot imagine it being a reason - it's an EXCUSE.

So, someone basically told you they don't love you enough to make a commitment. And they don't see you as your future, nor do they want to spend their lives with them. Would you continue being with them? Maybe you would, but I personally wouldn't.