You absolutely adore your girlfriend and now she needs space to think. You feel as though your heart has been deflated. You're confused, worried and anxious about what she's feeling or not feeling for you. Since she told you she wants some time you keep replaying your relationship in your mind. You wish there was something you could do to pull her back to you. You hate that things have gotten to this point and you're lost as to how to change any of it. Fortunately, there are some things that any man in your position can do to transform the dynamic of his relationship so his girlfriend wants nothing but to be as close as possible.
If she needs space to think try not to view it as the end of the world. Granted it feels that way given the fact that it means that she's rethinking the relationship. Space can actually be the catalyst for positive change in any relationship. If you overreact and get upset with her because she desires some time apart, you're just going to show her that she's right in wanting to separate from you. You instead have to show her that you respect her needs and that you recognize that some time apart is a good thing for you too.
When a woman wants distance it's primarily because something within the relationship just isn't working for her. You must therefore place your ego aside for now and really look at what is going on with you and your girlfriend. Think about what has made her unhappy in the past and what you can do now to change those things. As she's taking time to think you should be using that same time to make some positive improvements in the man you are.
Agree to the time apart and then be supportive as she's using the space to consider what she wants.