URGENT: Why is he avoiding me!?!?

Well, it seems obviously that she told him exactly what happened. As a drama queen (that what she seems like) she probably told him things she'd read etc. and questioned him on how he felt about her. Guessing she wanted more than just a friendship with him. He was probably shocked that you shared those messages with her feeling that those we kind of personal, even as friends, between the two of you. He clearly was never too interested in the new girl and your sharing the messages with her and his desire to distance himself from her all ended up being too much drama. He probably felt awkward about the whole situation too. So since he has now had a short conversation with you that at least felt normal you can work on extending the conversation next time. I'd distance myself from the new girl if possible..... unless you can really see her as a long term friend. As far as never seeing him again after June that is a possibility as he must be graduating but you can still remain snap-friends so try to gently resurrect the friendship. Keep in mind he's feeling sensitive right now but will most likely come back around if the new girl isn't there. I think this friendship is salvageable. IF he continues to act distant then..... depending on how good of friends you were with him in the first place..... you may just have to bring the whole thing up and have a calm conversation and explain to him directly what happened. Best of luck!