I'm sorry to hear about her dropping out of contact. I can't imagine what it would feel like. I know I start feeling anxious if my girl is half an hour late logging on.
I'm not really in a position to give advice, but I will tell you what I think about your situation anyway. We are most of us looking for somebody who will care for us and who we can care for. At the moment we don't know why your girlfriend has disappeared, and she may have a good reason. But if she doesn't have a very good reason for suddenly dropping out of contact for a week, then she is at best very insensitive, and possibly cruel. Not the kind of girl I would want to be in a relationship with. Perhaps you have been very hurtful to her without realising it, but unless you have been truly awful, even for this just dropping out of contact for so long seems excessive.
Because of this opinion, to me there is nothing wrong with your trying to ring her as much as you feel like till until you get an answer as to what is going on. When I ring up using one of those services where you dial another number initially, and then the number you want, then my number doesn't appear on her display.
To me, if is she is a good person in a difficult situation, she will be glad to hear from you, and if she is annoyed at your persistence, then she isn't worth the bother.
I realise that this is easy for me to say since it isn't my relationship I'm talking about. Good luck. I hope it works out for you. Please keep us informed.
Tom.