Okay...
She wants "to be single" for the summer. That should be your answer from her. If you feel you must communicate with her regarding this, just say you will "be single" also. No other explanation is necessary....like if you're seeing another girl! You may not feel ready to do this, and you sound very sensitve and honest, but since it sounds like she's "playing" you, that is really all the explanation you need to give.
Sometimes yoiu just have to take care of yourself first...be tough!...even in matters of love!
Patty