Funny how the exact same thing happened to me in october of 2010.
She too was stubborn, said she needed time on her own, couldn't specify how much time she needed...
I never stopped talking to her and we were still pretty much best friends during the following two months, but she never gave me a definite answer. Eventually, too much time had passed and she felt like she couldn't give me an answer after making me wait so long, and without ever speaking about our relationship again.
But turns out that the fact that I was always there for her without making her feel pressured, made her realize she had been terribly stupid. It was just that she was too proud to admit that she had made a mistake, and didn't have the courage to tell me that she still loved me.
I ended up noticing it, we got back together on new year's eve and we're still together, even though I felt like shit for 2-3 months.
That's what happened with me and everything worked out fine, but every case is different so I doubt anyone could give you proper advice. Good luck :c
/invade