I agree with "Thinker" ~ except that I read that you are 23, right? Anyway, definately get out start finding what you like to do, enjoy life. I know it's hard, especially when you feel lonely or hurt and are missing the person you love. But it is so much easier to pass time trying to enjoy life, even if you have to fake it at the beginning....it gets easier (dorky but true) By enjoying life, I don't mean you have to go out and date other girls..that would just complicate your situation.
Believe me, your girl, is probably very confused with life, not you. Maybe she feels "gee, I'm going to be 20 ~ what do I want to do with my life?"
She probably is doing a little searching, let her do it. It is better now than later. You should be happy that she was honest with you and told you what she needs, instead of stringing you along pretending everything is okay. She needs this time....support her by letting her "live" but be her friend ~ remember this isn't a personal stab at you, she needs to grow and mature. (19/20 is still very young)
And best of all for you, please enjoy yourself, travel if you can, read, do the activities you enjoy! Learn to be happy and content by yourself, heal.
Blessings to you! Hope it helps.....if you need anything else we're here to help....