I don't want my boyfriend to talk to this girl? Am I wrong?

[γοςςjνα]

My boyfriend and I have been together for 10 months. One day I got on his facebook and read over 500 messages from this new girl at our school. I called him crying and all upset because they were definitively flirting with each other. He said our friend got on his facebook and was the one talking to her. My thought was she still THINKS my boyfriend is the one talking to her.

and I know it wasnt only our other friend talking to her, my boyfriend was too. He also liked a bunch of his pictures.

So anyways he was all like "I wont talk to her, I'll delete her" and so we messaged her saying " I cant talk to you anymore, my gf wont let me. She left it alone for about 3 weeks and on Wednesday she messaged him saying "hey".

What should I do?