It seems your girlfriend was pretending she loved you for the six months which is a common phenomenon. It might be she loved but was either forcing herself or her feelings for you began fading.
You should arrange a day (after not contacting her for a few days) to talk through the issue. If she agrees and maintains her stance, you'll have to accept it. If she doesn't respond to meeting each other, wait for another few days before contacting her. Later, ask her to meet and talk. If she still refuses, it's time to move on.
However, it's evident something might have led her to no longer have feelings for you or she never loved you from the beginning.
I would suggest you accept the fact and move on with your life. It's difficult but you can make it.