I am sorry about the delay.
Since you have posted so much information, I am going to go through this step by step.
Based upon you mentioning that she is left for college, I am assuming you are both in your late teens or early twenties. The ebb and flow of relationships is normal in this age range, especially when they are as intense as you describe yours.
It seems like the two of you have different needs as far as connecting, based on your description of yourself as "needy" and your girlfriend seems to need a bit more space. In order for this dynamic to last for the long-term, the two of you need to sit down and set parameters around the amount of time you are going to spend together and figure out if you can trust each other to act autonomously.
It appears like your girlfriend is attracted to you and is attached to you, but she still seems like she needs time to explore before she settles down.On the other hand, you seem to be in a place where you are ready to make a commitment.
Sharing the loss of a child, even through miscarriage, is something that can bond two people together for a lifetime. It might be this bond that keeps drawing you together.
To answer your original question, can the relationship be saved, I think the two of you have the basis for a lifelong friendship. I think your girlfriend has sent some pretty strong signals that she is not ready to commit to a long-term relationship at this very moment, but there is potential for the future.
Please let me know if I can clarify anything, or if you have additional questions, if not please accept by answer.