I would have to agree. That is some peculiar behavior, but i couldn't say if she has aspergers or not based on the information you have given. Since you have stopped communicating with her, it really shouldn't matter anymore, unless your still interested. If your still interested try communicating in a very direct manner, and ask her questions about why she is shutting you out from her friends, and being possessive with you. If she has AS than she probably isn't very good a communicating, which leaves it up to you to initiate any communication.

Good luck