Just Friends?

Kayla
So my boyfriend of four months and I are about to graduate. Last year (our junior year) he asked out this girl from another school who was a sophomore. this was the first girl he ever asked out before. he really liked her & recently claimed to me that SHE was her first love. but she rejected him and said she just wanted to stay friends but right before my boyfriend asked me out this year she tried to get with him but he said he already liked me. a month after we started dating, (I forgot to mention that the girl and I are friends) she messaged me and told me that she doesn't understand why he chose me over her. she and I are not friends anymore after this conversation. he snapchats her and text messages her still. (she has a bf also) and I'm curious to see how other people view this situation. please let me know if I'm being an overly protective crazy girlfriend or do I have a reason to worry about this.