There are 3 reasons why your girlfriend would want a break:
(A) Her attraction level has dropped below 30%. Women do not break up with their boyfriends when their attraction level has gone below 50%, they will instead choose to torture you and withdraw sex. If you sense your girlfriend’s interest level going this low, then you need to exit your relationship or risk dying a painful death. In this scenario, you have no hope. Attraction is like a rubber band, once it snaps, it’s done. Cut your losses and move on, don’t make the same mistakes in your next relationship.