What do you do if your girlfriend up and left you without any prior notice? She may tell you she just needs a little space to herself to sort out some things.
Now you are trying to figure out what has happened to bring this on and can't find a reason.
Also, how much time should you give her? It's very possible that she needs to have some time to herself, maybe she's overwhelmed by something and needs to think it through, maybe even family issues.
About all you can do now about it is let her have her time to herself.
No use arguing about it because it will only make her angry and feel restricted.
If you try to talk her into telling you why she's doing this, you again will be putting her on the spot and she may not want to talk about now.
If you think you have had a strong relationship then you should not worry too much about her taking off, she should be back with you soon.
If she is gone a week then I would at least send a text message to say hi and that you are thinking of her.
Don't pressure her to come back or explain her actions, you can talk it over later.
If you get a friendly answer back then you should have nothing to worry about.
If you get no replay, try to contact her again in a couple days.
If you get a chance to talk, just let her know you are thinking of her and that you love her.
Let things take there natural course.